Meet Meredith Grey. Daughter of famous surgeon Ellis Grey and currently recovering from a one-night stand. She shoos away her evening's companion, saying she'll be late for her first day of work. She is a first year intern at Seattle Grace Hospital and is working alongside some colorful characters. Cristina Yang is a highly competitive Stanford graduate who befriends Meredith. George O'Malley is a quirky warm hearted man who learns a lesson or two on his first day. Izzie Stevens is a former model who doesn't get any special treatment on her first day. And Alex Karev is an arrogant jerk who misdiagnoses a patient on his first shift. Overseeing them is Miranda Bailey, (not-so-) affectionately dubbed 'The Nazi'. Meredith also gets a surprise when she realizes that her friend from the night before is a co-worker, and even worse, her boss.

The surgical staff tries to be optimistic as a young woman clings to life after a brutal attack. Meanwhile Meredith puts her career on the line to save a newborn in the hospital nursery, and the other interns learn that it takes more than just medical knowledge to be good at their jobs.

A bike race injures several pedestrians as well as well as participants. One pedestrian is left brain dead. Christina and Issie wish to use his organs for organ donation but with Christina's detachment and Issie's ever hopeful attitude that the man will recover, they will find the organ harvesting process an emotional one. Preston faces feelings of his dislike of organ harvesting - as a surgeon, he likes saving lives; harvesting organs doesn't save the person's life. George deals with Mac, a friend of the chief, who won't stop flirting with him. He is in need of a new liver. Meredith is fed up with Alex showing off as she continues trying to push Derek away. She also is reaching the limits of Issie's sunshine and George's politeness as she goes on living with them. Then there is their desire to see Meredith's mother's medical tapes. Getting through the day, Meredith realizes the keys to winning the race.

While George is feeling a little less masculine because of the way Izzie and Meredith have been treating him (like a sister), Izzie is assigned to a patient about to loose all of his masculinity. Cristina, true to her competitive spirit, shows up early and assigns herself to an ill woman, who happens to have been Meredith's moms scrub nurse. Alex, meanwhile, is busying himself copying and pasting pictures of Izzie's racy magazine spread all over the interns' locker room. And while Meredith is trying to cope with her mother's Alzheimer's, Derek treats a patient who has managed to get nails stuck in his head.

Meredith realizes that she must take on a lot more responsibility when she is told that her mother needs to sign over all of her assets to her. As Izzie prepares to have a party for her boyfriend Hank (the scale of which is unknown to Meredith), Meredith has her first heart surgery. During the surgery she fears that she has fallen asleep and damaged the patient's heart. Meanwhile, Cristina and Burke hit it off. At the party, Meredith and Derek get caught together by Dr. Bailey.

Izzie tries to get George to find the courage to ask Meredith out. All of the interns are in awe when a woman comes in with a record breaking tumor, but it is so far advanced that the woman's prognosis is not good. Now that Bailey knows about Meredith and Derek's affair, their jobs are in jeopardy, and she advises Meredith to end it. Meanwhile, Cristina and Burke's secret relationship is also getting more complicated...

Derek and Meredith try (unsuccessfully) to be discreet as they spend the night together at Meredith's house, but their haggard appearance speaks volumes to everyone - including Bailey, who warns Meredith to end the relationship. Meanwhile George suspects an anesthesiologist of drinking on the job but is reluctant to speak up about it, Alex treats a former competitor who now finds honor in self-mutilation, Izzie has to deal with a patient who won't let go of his girlfriend - literally, and Cristina seems to be battling a case of the flu.

Meredith grows increasingly dissatisfied with the unknown details of Derek's life. Meanwhile, Alex treats Devo, a patient whose religious beliefs jeopardize her chances for recovery; Izzie contemplates reconnecting with her estranged mother; Zoey, a pregnant woman in her 40s who's been diagnosed with cancer, disagrees with Cristina's medical advice; and the interns are mystified by Cable, a patient who's being treated for seizures and who thinks he's psychic.

A sexually transmitted disease breaks out and affects several members of the hospital staff. Chief Webber promptly calls a meeting. Meanwhile, the chief reluctantly tells Dr. Derek Shepherd about his own medical concerns. Izzie and Cristina worry about a patient's wife and daughter who can't agree on his care. Burke treats his college buddy Bill, whose medical diagnosis raises some questions regarding his wife's actions. Then just as Meredith and Derek grow more intimate, a surprise is revealed.

Picks up where the last episode left off. Meredith attempts to work with Addison Shepard. George is pimped out to relay the hospital gossip back to Webber. Meredith and Cristina relate at Emerald City Bar about what dating their respective attendings is like. Cristina ponders her relationship with Burke while trying to make a decision. Meredith is devastated by the latest blow to her love life. Meanwhile, Joe the bartender collapses.

There's tension between Meredith and Addison. We find out why Derek and Addison aren't together. Bailey puts George on an impossible case. The rest of the interns operate on a family that was just in a car accident.

Cristina and Meredith try to figure out if Cristina should tell Burke that she's pregnant right before Cristina faces an emergency. Alex and Izzie get closer while Meredith's mother gets too close.

As Cristina tries to recover, she proves to be a very difficult patient, and a visit from her mother doesn't improve her demeanor any. And Meredith's mother, Dr. Ellis Grey, has the hospital staff running in circles.

Cristina goes right back to working right after being discharged. Izzie isn't talking to Alex. Derek and Meredith treat a patient. George and Alex get stuck in an elevator.

Train Wreck victims come to Seattle Grace and all staff gets called in. Everyone deals with really weird cases. Except Addison and Izzie. They work with a woman who is pregnant.

Cristina, Izzie and Meredith take care of Shane, a man who appears to be crazy and claims that he is pregnant. Shane's case induces a spreading fascination among the staff. George relates to a patient's husband.

Meredith tries to avoid the Shepherds. Cristina and Burke go out on a date and end up getting caught up in their jobs. Derek asks Meredith not to ignore him until Addison comes walking around the corner.

It's Thanksgiving at Seattle Grace Hospital but the holiday's festivites are less than in order. Meredith and Derek try to counsel a family after their relative has had a seriously traumatic accident.

Dorie Russell is waiting for quintuplets, all 5 girls. Her husband seems more concerned than she is but she is set to bring her babies to their term of 36 weeks. All the departments are on call for the quintuplets as three of them have developped problems of different kinds. Meredith last night's stand shows up at the hospital with priapism and they need to call Derek Sheperd for a consult which puts Meredith in a very embarassing position. Alex and Derek must take care of a patient who has a tumor inducing thirst as a side effect. On the love side, Alex and Izzie are having some slight sexual problems, while Meredith goes on adding one night stands and Cristina is thrown off course by being "keyed."

Cristina Yang has little sympathy for Constance Ferguson (special guest star Rosanna Arquette), a prison inmate who jeopardizes her health just to get out of solitary confinement. Meanwhile the interns all keep careful watch on the family of premature quintuplets with a variety of serious health challenges, Izzie's anger at Alex reaches boiling point, and Dr. Addison Shepherd decides to teach Izzie a very painful lesson.

The holiday season has started but not everyone is in a festive mood. This is Alex's last day in the hospital unless he passes his boards practical exam the next day, thus everyone helps him to review so that he succeeds. However, Izzie is not happy about the others helping him and Meredith has to remind her of the true spirit of the Christmas holiday. Justin is in need of a new heart. One is available but he does not want it because he does not believe Santa gave it to him as his mother said. Cristina and Burke, both handling Justin's case, have opposing views on the matter due to their different stances on religion. Despite a reconciliation with his wife, Derek isn't in a festive mood. George has a simple case of a woman who has a bleeding ulcer, he realizes that the ulcer is caused by her entourage but fails to keep them away, with the consequence that it perforates.

Cristina is bothered by a new year's mandatory work limit. Izzie patient, Denny Duquette, wants two things: 1. a heart transplant, 2. Izzie. Addison detests Derek's trailer, Derek visits Meredith's mom, George treats a young teen hermaphrodite frustrated by her pre-pubescence. Other news includes patients doing uncanny things and relationship havoc being wrecked between the doctors, as per usual.

Meredith and Cristina lie to each other and themselves about their relationships with McDreamy and Burke, respectively. George is given a hard task to expel a discharged and defiant woman from the hospital. Alex learns his fate after re-taking his medical exams. At the same time Izzie is trying to stop Alex from making stupid decisions when a patient that doesn't speak English is lied to by her coach. George, Cristina, and Alex compete in a hot dog eating competition.

All the nurses at Seattle Grace Hospital go on strike, leaving the doctors to fend for themselves. George refuses to cross the picket line and finally joins the nurses on their strike while Alex, Cristina, Izzie and Meredith meets Bailey's stand-in: Dr. Cindy Aaron, the complete opposite of Miranda Bailey. Izzie agrees to work on a difficult pregnancy case with Addison, while Cristina and Alex are in the pit attending to a young married woman with a real bad case of rash. Meredith happens on an old woman that she needs to intubate and then learns she was DNR.

An explosive case arrives at the O.R. that might endanger all the lives of the people working there, which leads Dr. Burke to declare a "Code Black" for the hospital. Bailey worries where her husband is as she is in labor. Also Izzie and Alex may be creating some heat.

Derek is still operating when he finds out about Meredith's current situation. Meredith is freaking out about her situation. Webber and Bailey are dealing with medical health issues. Cristina and Izzie have their own issues to deal with because of Meredith's situation. Addison freaks out when George tries to find a solution to Bailey's impromtu postponement. Overall, Seattle Grace Hospital is still under code black and the situation is getting worse.

Derek and Addison's relationship is rocked to the core when a former friend comes to Seattle Grace and his presence promises to shake things up for a few members of the staff. Burke and Cristina's relationship is affected when one of her secrets is outted. Alex and Izzie are having similar reactions to their closet scenes during the Code Black crisis. On top of this a cocky doctor shows up to piss Derek off in all kinds of ways. A patient is suffering from constant orgasms and her condition sparks interesting conversations among the staff. George is trying to figure out how to get Meredith to see him as more than just a housemate. Another patient, that Derek is treating, is dealing with a rare disorder and needs his parents support and understanding. Burke has a patient who inspires him to talk to Meredith and Cristina about doing what they say they will. Meanwhile, Meredith learns more about her family (in fact maybe more than she may have wanted to know) through her parents.

Meredith and George are experiencing morning-after tension at home and at work and it has the rest of the doctors wondering what's up. Derek and Addison are experiencing their own version of morning-after tension as a result of Mark's visit to Seattle. Bailey, returning the favor that was done for her during the Code Black situation, must treat Addison for a specific feminine problem. Izzie and Alex are making headway in their relationship until Denny Duquette comes back. Soon Alex is not-so-oddly jealous of the attention Izzie is showing to Denny. Someone finds comfort in confiding in a patient who is going through an ordeal of his own. Burke deals with a patient and gets to observe the patient's unstable relationship with his fiancée.

The doctors are up to their necks in their usual levels of drama. Meredith is dealing with the backlash of sleeping with George, George and Burke are bonding in ways that bother and creep out Cristina, Cristina gets stuck on diaper duty, Bailey gets involved in a case even though she's still supposed to be on maternity leave, Addison and Derek have a talk, and Izzie is still flaking on Alex for Denny Duquette, the heart patient who didn't get a heart. In the patients-of-the-week department we've got a very pregnant woman, a hockey player who desires medically unnessasary amputation, and a woman with a fork in her neck who happens to be dying and has a struggling marriage.

After a series of deaths at the hospital some of the staff become very superstitious. Izzie worries about Denny and gets confronted by Alex. A patient with OCD drives Cristina crazy. Derek and Addison discuss their relationships with Meredith. Richard treats a friend from 17 years ago who reveals a secret about a dark time in his past that involves Ellis. George gets an earful about the women he's not talking to. Burke and Cristina argue about kicking George out.

Meredith and Izzie take up knitting. Derek operates on Andrew, a spelling bee champ with a serious head injury. Bailey gets in on Andrew's surgery because she's worried that her coworkers won't recognize her Nazi-status now that she's a mother. Addison's patient has an unborn baby with medical issues. After Alex fails to bite his tongue when a terminal patient routinely lies to her daughter about her health he gets a lesson in bedside manners from Burke. George also begins to overstay his welcome at Burke's apartment after Callie visits him. Meredith has more confusing and uncomfortable encounters with members of her family. One of the female doctors meets a veterinarian named Finn. Izzie flirts with Denny and they play more naughty-Scrabble. Meredith, Derek, and Addison sarcastically take another small stab at their friendships.

Addison's patient is a Catholic mother of seven. Addison gets in trouble after learning that the patient's husband won't use contraceptives. Derek treats a divorce attorney who asks if Derek is in need of her services. While Izzie and George are talking about their personal lives they "overhear" part of Derek's conversation with the divorce attorney who calls herself one of Seattle's best. Alex gets in trouble with Addison yet again for not being able to keep his mouth shut when other people think he should. A legendary jazz musician refuses to see medical reason. The musician is Burke's musical hero. Finn makes Meredith breakfast.

The staff attends to an intern from another hospital who has short-term memory loss. This intern, named Marshall, also has caused a car accident that involved a married couple, their unborn baby and the woman's parents who the staff are also treating. The pregnant woman is named Melanie and she will die but her baby may survive. One of the female interns meets up with a woman from her past who is planning on having a family of her own. Cristina is in a good mood although Alex, Izzie, George, and Meredith are having problems but in the meantime Burke hasn't forgiven Cristina for her late night faux pas. Meredith and Izzie are making fun of Callie's household habits and George and Callie are having a fight because of George's roommates. Addison is continuing to own Alex and he's upset about it. Denny has an outburst at Izzie and Derek has an outburst at Meredith.

George and Derek work together, Denny still doesn't have a heart, and Meredith gets paired with Callie. A 12-week pregnant girl dies in the O.R. and her parents try to keep the baby alive. This causes tension between Derek and Addison. One doctor's overreaction unites two bickering patients. Finn is still treating Doc for medical problems.

Denny needs a heart or else. Izzie and George go crazy trying to get him one. Derek has the life of a friend in his hands as he operates on Burke who has been shot. Burke cannot operate on Denny after Denny's heart stopped and now Denny is in a dire condition. Cristina gets put in charge of the ER and she is worried about Burke.

This episode is the second part of a two-hour season finale. Richard tries to get information from Addison about a family member's condition. Callie and George have a talk about his feelings. Meredith and Derek have a talk about Doc.

Meredith must make an important choice about which path she wants to follow to determine the future of her love life. While she considers her future she and others have flashbacks of their pasts. Cristina spends time with Burke while he recovers. Webber and Adele have a conversation after he spends the night at the hospital. Everyone attempts to deal with Izzie's choice to quit. George seeks relationship advice from Derek.

Cristina meets Burke's parents, the interns try to get Izzie's job back, and Addison takes a day off, a surgical patient may be living her last day. Some of the interns want to know why Bailey won't talk to Izzie. Meredith tries to decide between Derek and Finn and comes to a decision somewhat. Webber finds out that Callie has been living in the hospital and he confronts her about it.

The staff tries to prevent a patient from getting an elective surgery. Cristina tries to help Preston cope with the after effects of his surgery. A patient bails on their surgery. Someone goes to a bed-and breakfast. Alex deals with a patient who has had a high amount of injuries in the past. A man undergoes surgery. Before the surgery his wife was only somewhat supportive, but the results may be too much for her to handle. Izzie tries to go back to the hospital for the first time since Denny died. One child's constant visits are noted by a nurse. Two foster patients are met with suspicions of child abuse. George and Callie's relationship moves forward.

Shawn Sullivan, a car salesman who just had surgery, wants to get back to his routine so he doesn't lose his renown. Addison works with a pregnant woman named Rebecca who may need a C-section and Addison doubts her medical skills. Rebecca wants to have the baby naturally. Derek and Mark's opinions clash when the try to decide the course of treatment for a burn victim. Izzie gets surprised. Cristina pushes Burke to get better faster.

Derek learns one of Addison's secrets. Bailey talks about motherhood and depression to a mother who is set to have cancer surgery and who seems to not care about any decisions concerning the future. A resident is fiercely questioned about the death of a male patient. An ex-couple meet before lunch and get stuck - Meredith and Addison work on their case. Things get awkward when the ex-couple's daughter, Michelle, arrives at the hospital.

Cristina gets to scrub in on a rare surgery which incites envy. Alex questions his future in plastics. George and Addison work together with Noelle. Noelle is pregnant with twins but one of them is growing slower than the other. Her fiancé has problems of his own. Derek's sister visits. A patient's wife makes things hard on the staff since she has made her husband's health her job. A woman's sexual exploits are questioned.

The men of Seattle Grace go on a camping trip together, Addison and Callie must team up to work on a patient, Meredith assists Sloan with a procedure unlike any she has experienced, and, suspicious of her recent actions at the hospital, Bailey confronts Cristina. A 9-year-old is seen by Cristina after he swallowed Monopoly game pieces. A pregnant 25-year-old, is brought in after she slipped in the shower. She doesn't want medicine to take away the pain from her injury so not to put her baby's growth in jeopardy. Doctors take care of Daniel, a man who wants a sexual reassignment surgery and who now goes under the name Donna. Accompanying Daniel is his wife of the past 10 years, who was surprised to see him want that surgery but, after much struggling, decided to stay by his side.

George's father has a serious heart problem that requires surgery and George chooses Burke to do the procedure. Burke doubts himself because he knows the pressure this kind of surgery will put on him, but Cristina believes the team can handle it. Derek works with Meredith on being a couple again and tries work with Addison on more civil terms. A patient has had mutiple plastic surgeries so that his girlfriend will like him more. A mom wants her daughter's babysitter fired, after she is brought in with multiple injuries, but the girl likes the babysitter more than her mother.

A traumatic car accident fills the ER. Izzie pushes the boundaries of her probation. Cristina has a crisis of conscience about her deceptive teamwork with Burke.

Recent events strain Burke and Cristina's relationship. Mark and Derek must work together when two close-knit brothers seek medical help. One of Meredith's half sisters is admitted to the hospital.

Meredith discovers that Derek has a problem sleeping while her father comes to visit the hospital. George's father is moving from one surgery to another. A patient named Heather checks into the hospital. Heather is 17 and has a nasty attitude that results from her medical condition and all the surgeries it has required her to have. Izzie has an emotional breakdown when she tries to hand over something very important to her. George's family comes to visit to celebrate his father's surgery. Cristina and Burke are playing Uncle.

Cristina and Burke continue to play Uncle until one of them gives in. Derek and Meredith are fighting over the reason for their sleepless nights. Meredith tries to talk to her father about his side of the story. There's tension between Alex and Addison. There is even more tension between Addison and Mark. Addison confides in Callie. Bailey wishes she didn't have to keep a secret from one of the interns. Callie rushes to be with George after she learns that his dad needs an emergency procedure. Izzie may have found 'some good to do' with her inheritance.

After the Chief announces his retirement, rumors begin to circulate on his departure and successor. Mark is determined to leave Seattle for good but Meredith accidentally has him stay after letting him know of the open Chief position. Derek is angry at Meredith for causing Mark to stay in Seattle, but soon realizes that she is not the reason he is really angry. The attending physicians at Seattle Grace Hospital fight to get Richard's attention, but he expresses his disappointment. He also displays his lack of support in Bailey's plan to create a free medical clinic, but she ultimately goes through with her plan when Izzie offers to spend her entire 8.7 million dollar inheritance on the project. George, devastated after his father's death, uses sex to overcome his grief, and eventually proposes to Callie. Cristina and Burke still don't speak to each other, but he breaks the agreement when he proposes to her. Richard endeavors to reunite with his wife, Adele, and decides to retire, only to come home and find his wife with another man.

The race for the Chief's position is on, and the attending physicians, Derek, Burke, Addison and Mark, compete for Richard's affections by trying to help out everywhere possible. The Denny Duquette Memorial Clinic is open for business, but only one single patient shows up. Izzie is disappointed in what she invested Denny's legacy in, and tries to steal patients from the emergency room. Callie and George get back from Las Vegas, announcing their marriage, much to everyone's disbelief. Izzie is not supportive of their marriage and tries to get George to realize the mistake he has made. Meanwhile, Meredith's Alzheimer's-stricken mother, Ellis Grey, experiences a change in her medical condition by becoming lucid for the day. She is disappointed in the mediocrity her daughter has fallen into and begins to despise Derek, blaming him for what happened to the Meredith that used to be "a force of nature". Ellis has to have heart surgery and, despite her wishes, Meredith schedules her upcoming surgery. Richard talks to Ellis and realizes that she is still in love with him, but loses her memory after their talk ends, before Meredith has the chance to tell her how she really feels.

A mass trauma situation, which turns out to be a ferryboat accident, challenges the whole staff of Seattle Grace Hospital. Richard finds difficulty in coping with his separation from his wife and dyes his hair "for the ladies", which becomes an internal joke between Mark, Burke and Derek. Cristina tries to tell Meredith about her upcoming marriage, but doesn't have the strength to. George promises to find a woman's son, who has been separated from her at the accident. The woman refuses to go into surgery until she is assured that her son is alive. Izzie has to take care of a man who got stuck between two cars on the ferry, but nobody helps her due to the large number of injured people. Alex rescues a pregnant woman with severe wounds on her face, and promises to take care of her. Meredith looks after a girl who has been separated from her mother after the accident, but accidentally falls into the water and drowns, with nobody but the little girl as a witness.

Meredith is still underwater, but nobody seems to notice. Her worsening condition makes her rescuing an urgent matter. Derek finds her coat on a man she had helped, and starts looking for her and, much to his shock, the little girl Meredith took care of suggests that she is in the water. Derek saves her, but she is almost dead, due to hypothermia. Izzie has to perform brain surgery on a man stuck between cars, as he begins to experience seizures. She drills holes into his head, perforates his skull and ultimately saves his life before he is rescued and transferred to Seattle Grace Hospital. George lies to the woman whose son he had been looking for, in order to get to surgery, but still doesn't have any luck in locating him. Alex finds no hope in searching for the pregnant Jane Doe's family as she undergoes surgery. The interns find out about Meredith's situation and express their hopelessness. She wakes up in what appears to be limbo and meets her deceased acquaintances.

Everyone is pushing for Meredith to survive, or in this case to be revived. People are still dealing with the fallout from the ferry disaster. A young man named Lucas is having problems with brain-mouth coordination. Someone else dies.

The race between the attending physicians for the Chief of Surgery position heats up after a new competitor enters the fray. They soon realize that the new surgeon, Colin Marlow, was Cristina's professor in medical school and they used to have a long-term relationship. He begins to lie to Burke in order to protect her secret, but is soon faced with the realization that their relationship is on the rocks. George finds out that Callie's family is rich, but she had previously hidden the fact in order to find out whether George loves her for who she really is. Derek treats his former colleague from New York, and forces her to have surgery for brain cancer in order to save her future, no matter what the post-surgery risks are. Alex continues to work with Jane Doe, whose memory doesn't seem to come back. He moves in with Meredith and they have a dinner with her father and stepmother. She seems to connect with Susan, but her relationship with Thatcher seems to be irreparable. Izzie wakes up, realizing that she has slept with George while they were both drunk.

In the aftermath of Izzie's affair with George, he doesn't seem to remember anything. Callie lets him know that they will be having dinner with her father, but George does not make a good impression, being hung over after last night's events. Alex helps Jane Doe choose how her face will look like after Mark Sloan performs reconstructive surgery on her. He also gives her a new perspective on how the world will see her from then on. The hospital board begins interviewing the candidates for the Chief's position, and Colin Marlow intimidates everyone with his ten-year plan. However, after taking advice from Bailey, Mark seems to have convinced the board that he is appropriate for the job, despite continuous efforts from Derek, Burke and Addison, whose careers in the hospital outlast his. Izzie seeks advice from Addison about her affair, telling her sleeping with George felt right, despite him being married. Mark takes Meredith as his intern for the day in order to impress the Chief, something that Derek doesn't approve of, feeling that Mark has become manipulative.

Colin Marlow continues to try to get in the way of Cristina and Burke's relationship. The daughter that Izzie gave up for adoption needs something from her. This episode features a pro chess player, a flirtatious woman, and a mother named Mrs. Malone. Mr. and Mrs. Malone haven't talked to their daugther in a while because of their son-in-law. Someone goes to see a priest.

The attendings vie to be Chief. Two people who haven't slept together before, will. McSteamy's 60-day vow of chastity has a conclusion. We meet a boss, his assistant, and his wife. We also get to see someone being treated in the clinic. Derek has more questions about his relationship with Meredith. The chairman of the hospital board is admitted as patient. Callie confronts Izzie about her relationship with George.

Meredith works on her relationship with Susan and Thatcher. Cristina has to deal with her mother and Burke's. Alex continues to tend to Jane Doe/Ava. Meredith and Derek's relationship has a problem that needs resolution quick. Addison sees her god-daughter which leads to a job offer outside of Seattle. Derek has to perform surgery. Burke has a reservation about marrying Cristina. Many new people guest star in the course of Addison's road trip to California. Addison considers moving to be closer to her old med school friends until she discovers that drama she wishes to leave behind isn't exclusive to Seattle. Her friends who she thought had it all, are divorced. A pregnant woman must discover who the father of her child is.

Meredith works on her relationship with Susan and Thatcher. Cristina has to deal with her mother and Burke's. Alex continues to tend to Jane Doe/Ava. Meredith and Derek's relationship has a problem that needs resolution quick. Addison sees her god-daughter which leads to a job offer outside of Seattle. Derek has to perform surgery. Burke has a reservation about marrying Cristina. Many new people guest star in the course of Addison's road trip to California. Addison considers moving to be closer to her old med school friends until she discovers that drama she wishes to leave behind isn't exclusive to Seattle. Her friends who she thought had it all, are divorced. A pregnant woman must discover who the father of her child is.

The interns finally take their first year medical exams, the biggest test of their careers, and one of them is ill-prepared. Callie grows more suspicious of George and Izzie. The doctors treat a patient named Dale. Three mountain climbers are treated. Cristina works on her vows. Adele wants Addison to keep a secret from Richard.

The mountain climbers lie about the axe in their friend's head, telling Derek that it accidentally got there. During surgery, he and George discover that it was deliberately put there, and one of the climbers admit that he was trying to "put him out of his misery". Adele is saved after Richard finds her lying in the bathroom and is stabilized, but soon suffers a miscarriage. Richard learns Adele was actually pregnant with his son, not someone she had one night stand with. Bailey is disappointed to see that Callie is the new Chief Resident and begins to question her abilities as a surgeon. Richard chooses Derek as Chief of Surgery, but he refuses, telling him that he isn't done doing what he does best. Cristina and Burke's wedding day arrives, but Cristina won't stay out of the hospital. However, Cristina's nervousness results in Burke's realizing that he does not love the real Cristina and leaves her. Meredith and Derek are uncertain about their future and despite Derek admitting that she is the love of his life, they call their relationship over.

Entering their first year as residents, Meredith Grey, Cristina Yang, Izzie Stevens and Alex Karev now have interns of their own to mentor. Among the new interns are George, forced to repeat his internship after failing his exams, and Lexie Grey, Meredith's half-sister. Another two new interns will be introduced in this season premiere. And they'll have their hands full when a three-car accident sends multiple casualties pouring into Seattle Grace. Some of the doctors need to deal with new stressed out interns. A young boy brings his bleeding deer to the hospital in the hope a doctor will save her.

A patient is in the hospital because they fell asleep in a hazardous situation. A patient's home laboratory blew up in an apartment building and the victims flood the hospital. Alex investigates the cause of the incident by talking to a really old guy who lived in the building. Jane Burke shows up to deal with what her son left behind. Lexie tries to talk to Meredith. Callie is overwhelmed by her new position while Bailey is searching for things to do.

The doctors meet the world's oldest intern. Marcy brings in her son Henry because she finds his change in behavior suspicious. A patient named Connie may lose her vocal chords unless Mark and Richard can perform a radical new surgery. George impresses the other interns at work but at home he is trying to deal with his guilt about having sex with Izzie.

A face familiar to one of the year-twos shows up and dredges up issues that were never really dealt with. A teen soccer player needs counseling because of his father and surgery for an injury he sustained while playing the game. Another patient's, named Courtney, finds out that her cancer is back.

It's Halloween at Seattle Grace! There may be jokes, pranks, and/or scare tactics. Some of the women form a club based on an experience they all share. A man volunteers for what most of the doctors believe is an unnecessary surgery. One of the patients is in the hospital because they tried to carve a pumpkin in an unconventional manner.

A patient comes to the ER with a dream and a condition which may prevent him form realizing it. Two patients are competing to win something big. One of them convinces an intern to take their place.

Izzie and George's new-founded relationship results in them having bad sex. Callie's Chief Resident position is taken away from her, and Bailey is the humble replacement. Meredith can barely handle it with Lexie anymore.

There has been a bus crash and the patients are in the ER. Meredith and Derek's relationship gets more complicated when he dates a fellow doctor. Meredith's dad goes to visit her at the hospital.

An ambulance crash endangers the lives of the paramedics involved, as Meredith and the Chief work on-site to save them, Bailey treats a patient who refuses her help, and Ava returns for Alex and meets his other girlfriend in the process.

Meredith works furiously to save a paramedic trapped in an ambulance; Lexie holds the life of a patient in her hands; Derek must rely on a nurse to save a patient; Bailey struggles to balance her personal life with her work.

George has a surprise visitor. Bailey's family is falling apart. Derek sorts through what kissing Rose means. Meredith discovers something that doesn't inspire hope or happiness in her. Alex treats a faith healer.

Time has passed but not much has changed. Sexual angst still runs rampant in the halls of Seattle Grace. Derek and Rose have been dating and Meredith has noticed the activities of her current off-again ex-boyfriend. The doctor's are in the midst of a competition.

Addison visits Seattle Grace because they need skills that only she has. Rebecca/Ava returns with news for Alex. Meredith and Derek's clinical trial experiences one or two developments.

The clinical trial continues to make progress. The anti-McSteamy club creates new initiatives but that isn't enough to stop one woman from spending time with him. Christina is affected by Burke's career developments.

Dr. Wyatt refuses to let Meredith give up on therapy. Alex learns something else about Rebecca. The Chief wants Erica to perform a daring surgery. Christina continues to act strangely.

A couple undergoes surgery. Derek and Meredith's clinical trial gets a second shot from a new patient. Izzie helps Alex. McSteamy hooks up with someone.

A couple undergoes surgery. Derek and Meredith's clinical trial gets a second shot from a new patient. Izzie helps Alex. McSteamy hooks up with someone.

As Meredith and Derek begin to find that their "happily ever after" is anything but easy, Cristina develops a crush on a military doctor who brings in a trauma patient. Meanwhile, the Chief and his staff cope with the news that Seattle Grace is no longer considered a top-tier teaching hospital.

Alex is offended when Izzie talks about how great a man Alex is to Meredith. Derek is stabbed with the scalpel in the palm of his hand by Rose, while the Chief is stunned over Mercy West's increase in the number of patients, a deadly ice storm ravages Seattle.

When the plumbing springs a leak, chaos breaks out at Seattle Grace as the Chief tries to put in place new teaching methods. Meanwhile, George takes his residency exam; and Derek attempts to get Meredith's roommates to move out, much to their surprise.

Meredith is sent into a state of panic when Derek finds her mother's diary in the house. Meanwhile, Callie stresses while preparing for her first date with Erica. Later, Cristina stumbles across a part of the hospital no one has ever seen before.

Bailey heads up a "domino procedure" in which each surgery hinges on the one preceding it. Meanwhile, Derek gets sole credit for the brain-tumor study he did with Meredith; Lexie tries to get George to notice her romantically; and Sloan counsels a desperate Callie in the ways of love.

The chief gives Bailey new power and responsibility. He also gives her a very difficult surgical assignment: remove a girl's inoperable tumor. Meanwhile, new trauma chief Owen (Kevin McKidd) challenges the attendings' methods and the residents' skills.

When the Chief makes an announcement that a solo surgery is up as an award, the residents are sent into a frenzy all trying to get an edge over one another. Meanwhile, Derek asks Bailey for advice after Cristina continues to interfere in his relationship with Meredith. Elsewhere, Erica uncovers a shocking connection between a resident and a patient.

One of Meredith's oldest friends, Sadie, becomes an intern at Seattle Grace, but Mer's friends are less-than-welcoming to her.

Meredith, Cristina and Bailey come to Lexie and Sadie's rescue when a routine surgery goes horribly wrong, as Owen and Derek treat a man seriously injured while sleepwalking and Mark comforts the sleepwalker's distraught daughter.

Cristina is awarded the first solo surgery among the residents, but she is forced to give it up and choose her replacement; Lexie is impressed when Mark performs a cutting-edge procedure; Callie doesn't know if Sadie is friendly or flirtatious.

Bailey teams with Seattle Grace's new pediatric surgeon, Dr. Arizona Robbins, to save the life of a young patient near and dear to her heart, as the admittance of a death row inmate at the hospital stirs anger in Derek and further erodes Meredith and Cristina's friendship; meanwhile, Callie and Sloan work as a team to fight their respective attractions to Sadie and Lexie, and Izzie tells Alex that she's seeing Denny.

Derek's mother, Carolyn, makes a surprise visit to Seattle and meets Meredith for the first time, as Mark tries to conceal his relationship with Lexie from her as well; meanwhile, death row inmate William wishes to donate his organs to Bailey and Arizona's patient, as Owen and Cristina try to go on their first date.

Bailey grows desperate as a patient's condition becomes more and more dire. Everyone in the hospital is stepping up to try to find the boy a new organ donor, including Meredith, who considers a death row patient's wish to die before execution. Meanwhile, an injury leaves Mark in a compromising position in the OR and Cristina awkwardly avoids Owen.

Now that Derek has the engagement ring, he searches for the perfect way to propose to Meredith, as Lexie demands that Mark go public with their relationship, and Bailey, encouraged by her work on recent cases and by Dr. Dixon, considers a new direction for her medical career.

Addison, Naomi and Sam rush the ailing Archer to Seattle Grace and reunite with old friends Derek and Mark to help save his life; meanwhile, Izzie employs her fellow doctors in a medical game designed to help teach the interns, and Owen runs into a significant someone from his past

Derek's confidence is shaken like never before as he faces off with Addison over what course is best for their dying pregnant patient; Cristina calls the abilities of a renown surgeon into question after she botches a standard procedure; and Bailey, who has decided to pursue a fellowship in Pediatrics, is appalled by the Chief's less-than-stellar recommendation letter.

Derek decides to quit after learning that more of his patients have died than survived; Izzie's interns make an unsettling discovery about "Patient X."

After his fellow surgeons try and fail to bring Derek back to work, Meredith must summon the strength to convince him. Meanwhile the hospital is abuzz as Mark attempts a rare face transplant surgery. Cristina, at last awarded her first solo surgery, is more focused on the needs of her friends, and Izzie does her best to keep her medical condition a secret.

All eyes are on Derek as he is set to perform his first surgery after his breakdown; attention is also set on Izzie, whose medical condition requires her to undergo a difficult surgery; and Owen has another PTSD episode that injures Cristina and traumatizes both of them, throwing the future of their relationship into question.

As she endures aggressive treatment for her cancer, Izzie throws herself into planning Derek and Meredith's wedding.

As preparations continue for Meredith and Derek's wedding, Izzie receives a surprise hospital visit from her handful-of-a-mother, Robbie. Meanwhile, a newly sober Thatcher visits his daughters, Meredith and Lexie, in order to make amends, and the Chief and Meredith bitterly fight over a controversial medical case.

As Meredith, Derek and all of their friends prepare for the big wedding, a group of college students, injured in a car crash as they were heading to their graduation ceremony, is admitted to the ER. Meanwhile, Izzie fears the worst when she begins experiencing familiar symptoms.

In the first part of the two hour season finale, Izzie spends time with a fellow cancer patient and contemplates whether or not to undergo a risky surgery, as Mark is ready to take his relationship with Lexie to the next level and a patient makes Owen reassess his place at Seattle Grace.

In the second part of the two hour season finale, George delivers stunning news to Bailey, sending shockwaves throughout the hospital, and Izzie's friends anxiously await her recovery from surgery. Meanwhile Bailey is surprisingly displeased after being accepted into the pediatric fellowship program, and the victim of a near-fatal traffic accident brings the talents of Seattle Grace's doctors together. This is the second hour of a 2-hour season finale.

The hospital staff is left to deal with the aftermath of George's passing. Hitting the staff hard, they all find unique ways to get through the various stages of grief. George's mom returns, faced with the difficult task of deciding what to do with his organs.

Everyone is struggling after losing one of their own and are turning to any distraction they can find. Meredith and Derek seem to be consummating their marriage anywhere and everywhere, while Cristina and Owen have been instructed to abstain from sex by Dr. Wyatt.

Several weeks after her near-death experience, a recovering Izzie returns to work. Meanwhile, nervous that there will be layoffs in the hospital in the wake of an announcement from the Chief, the Seattle Grace residents compete to survive the cuts, including Cristina, who attempts to work alongside Arizona in pediatrics. And Bailey and Alex's patient's already complex case is further complicated by her schizophrenic son.

When Meredith and Lexie's father, Thatcher, returns to the hospital with a failed liver, it's up to Meredith to save his life. Meanwhile, Izzie empathizes with a patient riddled with tumors, as Mark, annoyed with Cristina's competitive zeal, tricks her into assisting on an unusual surgery.

The residents of Seattle Grace and Mercy West vie for surgeries and their careers as day one of the hospital merger begins. Meanwhile, Arizona stands by an enraged Callie when her father, Mr. Torres, employs a priest to help convince her to date men, and Izzie experiences the brunt of her new surgical competition.

After a burn victim unexpectedly dies in the midst of a chaotic ER, the Chief and board member Jennings interrogate the residents to find the culprit, as all the Mercy West and Seattle Grace resident defends their actions in an effort to save their jobs.

When Isaac has an inoperable tumor wrapped around his spine, he wants Derek to do the impossible. Derek tests the Chief's authority when Richard objects to moving forward with the risky surgery.

A generous 25 million donation is offered to Seattle Grace by the parents of Arizonas 10-year-old patient, she finds herself in a conflict of interest when his condition worsens. Cristina tests her boundaries with Owen at the hospital. Alex is left with all of Izzies hospital bills to contend with.

Owen recruits Dr. Teddy Altman, a former Iraqi veteran, as the new cardiothoracic surgeon. Cristina questions her abilities in the E.R. and relationship with Owen. Izzie returns to Seattle Grace with her high school mentor seeking treatment for his dementia. Richard's responsibilities, post-merger, are taking a toll on him.

As Thanksgiving, Christmas and New Year's pass, Miranda gets a visit from her father, William who disapproves of her choices in life. Mark and Lexie cope with an arrival of a woman from his past. Thatcher questions the Chief's recent behavior as Meredith comes to his defense.

Mark flies Addison to Seattle to help with a difficult procedure on his pregnant daughter, Sloan, Owen questions Teddy's motives when she assigns Cristina the lead on a complicated surgery, and Derek's suspicions are raised when the Chief recruits Meredith to assist with a high profile operation on.

After learning of Richard's drinking problem, Derek confronts him for the sake of his friend and the hospital, Izzie returns, hoping to reconcile with Alex, and tensions run high between Teddy, Cristina and Owen in the aftermath of Cristina's startling confession.

As Derek begins his role as interim chief, he faces a potential lawsuit when Bailey and Meredith's patient awakens from anesthesia mid-surgery. Meanwhile, Teddy refuses to place Cristina on her service, as Arizona tests Alex out in Pediatrics, and Mark refuses to speak to a heartbroken Lexie.

It's Valentine's Day, and the doctors must treat dozens of injured people after the roof collapses at a popular romantic restaurant; Derek tries to manage his busy schedule as Chief of Surgery; Meredith wrestles with her new duties as the Chief's wife; and Mark and Callie team up to convince Sloan to do the right thing for her baby.

In his new role as Chief, Derek restores the hospital lecture series, and Richard, Bailey and Callie present to the group pivotal surgical cases from their pasts Bailey reflects on her first days as a shy resident, Callie looks back on a polio case, and Richard recalls a case in which he and Ellis worked on a patient diagnosed with GRID, a virus later called AIDS.

When famous surgeon Dr. Harper Avery is rushed to Seattle Grace-Mercy West, the staff is surprised to discover that one of their own is related to this legend, and his unorthodox request for his surgery causes tensions t between Derek and Richard. Meanwhile Callie and Arizona try to help Teddy and Sloan move on from their pasts and find greener pastures.

A patient who needs an extremely difficult surgery comes to Seattle Grace, and it's Richard and Owen who vie for the opportunity to tackle it. But the decision lies in the hands of Derek, who deems that Owen should take on the surgery, leaving Richard bitter. Meanwhile, Bailey deals with her own personal struggles when she nervously prepares for another date with Ben.

When Teddy's patient seeks to end treatment and her life, she turns to Hunt for help. The situation triggers Hunt's memories of his life at war and his past relationship with Teddy. Meanwhile, Callie and Arizona have a difference in opinion on what their future holds, and Richard tries to adjust to his role as a surgeon.

When Alex's younger brother, Aaron, shows up at Seattle Grace-Mercy West with a hernia, it's up to Alex to get Bailey's approval for his pro bono surgery. Matters are further complicated when Aaron discloses that his family has not heard from Alex since he arrived in Seattle, and parts of Alex's past long kept secret are revealed to his friends and fellow doctors.

Sloan returns to Mark's apartment, just as she's going into labor, and Teddy, Mark and the still-fighting Callie and Arizona are there to help with the birth and to get Mark through his grandson's pending adoption. Meanwhile Teddy sees Derek's invitation to illustrious cardiothoracic surgeon Tom Evans' as a threat to her future employment at the hospital, and the team work on a crab boat captain who has been stabbed with a giant shark hook.

Bailey preps the team with mandatory sensitivity training prior to admitting a 700-pound patient with compounded medical issues, and the case proves to be challenging in every sense of the word. Meanwhile Derek has to come face to face with a former patient's husband in a wrongful death deposition, and spending time with a heart patient's daughter opens up some old wounds for Cristina.

An elderly patient admitted into the E.R. for a heart condition sees a familiar face, a long lost love who happens to be in the E.R. as well for a fractured arm, and the staff find themselves caught up in their love story. Meanwhile, Karev treats a troubled teenage patient (guest star Demi Lovato) whose parents brought her in for schizophrenia, and Meredith can't help but tell Cristina about her suspicions of Owen -- which inevitably messes with Cristina's head.

Seattle Grace Hospital is hit with a crisis like no other in its' history.

Cristina and Meredith's surgical skills are put to the ultimate test.

In the wake of the shooting at Seattle Grace-Mercy West, the doctors find themselves in a frenzy: Christina and Owen will be getting married, and others are trying to deal with the recent blood bath. Derek is arrested for speeding!

Meredith finally tells Derek about her pregnancy and miscarriage; during a surgery, Cristina experiences PTSD; Bailey won't let Alex operate until he has the bullet in his chest removed.

Issues surface when Derek's estranged sister, Amelia (Caterina Scorsone), visits unexpectedly; Meredith and Derek continue to try to ease Cristina back into surgery.

Derek and Meredith visit the obstetrician and receive disturbing news; Lexie notices April and Meredith growing closer; Jackson tries to get ahead in the operating room.

As part of their training, Seattle Grace's residents are put in charge; the attending surgeons compete for a million-dollar grant.

A documentary crew visits the hospital six months after the shooting to document the road to recovery for doctors and patients; Meredith helps Cristina put on a brave face for the cameras.

Owen puts the residents through a rigorous trauma certification drill; Cristina is left alone to monitor an ill lung transplant patient.

A team of doctors tries to save the life of a political figure from the Middle East; Cristina decides to decorate her new place and throw a housewarming party; Alex shows up late to his first day of rounds with the new pediatrics attending.

The residents are on their own with the dreaded night shifts while the attendings go out to play to celebrate Derek's grant for his clinical trial.

Derek takes Cristina out on a fishing trip; Teddy tries to help a patient who lacks the proper insurance to seek medical treatment.

A gunman opens fire at a local college, sending mass casualties to the hospital; Arizona's return is not warmly received.

Arizona tries to reconcile with Callie, who has big news to share; Teddy faces an important decision; the residents receive new interns; the Chief makes an announcement.

Derek breaks ground on his Alzheimer's clinical trial and Meredith can't help but feel left out; Bailey's attempt to take the hospital into the age of new media with live tweets from the OR does not go over well with the Chief; and Callie, Mark and Arizona must learn to navigate through the pregnancy together, which starts off with Callie driving her new obstetrician crazy.

Thatcher Grey, Meredith and Lexie's father, returns to Seattle Grace with stomach pains and a new, twenty-something tattooed girlfriend, Danielle. Meanwhile, Alex clashes with the new OB, Dr. Lucy Fields, over a patient and Mark places Jackson on his service in exchange for information on Lexie.

Meredith, looking to prove she is Chief Resident material, learns that anything and everything can happen in an hour's time when she steps up to run the ER for a night; meanwhile, Bailey sneaks off with Eli and gets into a little mischief, and everyone is surprised when the Chief's wife, Adele, shows up as one of the ER patients.

Meredith must choose between her fertility treatments and her eyesight when she begins having trouble seeing, Mark makes it clear to Callie and Arizona that he takes his role as father-to-be very seriously, and April discovers there's more to Dr. Stark than first appears.

Richard is desperate for Derek and Meredith to accept Adele into their Alzheimer's trial, but will Adele stand in her own way? Meanwhile Mark and Arizona have conflicting ideas of the kind of baby shower Callie wants, Teddy is freaked out when Henry has another health complication -- leaving them both a little exposed -- and the competitiveness amongst the residents for the Chief Resident position is amplified when Richard receives the green light for his diabetes clinical trial.

A cataclysmic event leaves the doctors shaken; Callie, on the verge of a life-changing moment, starts imagining about the hospital and her friends.

Everyone pulls together to help Callie and baby Sofia on their painstaking journeys to recovery in hopes of allowing mother and baby to finally meet; the sudden death of a clinical trial patient has Derek proceeding with more caution while Meredith makes a calculated and risky move; Alex treats a cranky old rich woman dying of cancer and gets an idea for a grandiose endeavor that is sure to get him the Chief Resident spot; and Teddy is pleasantly surprised by the return of a familiar face.

As Callie and Arizona's wedding approaches, the couple quickly realize that the day they've been looking forward to is not turning out the way they'd envisioned. Meanwhile Alex continues to make the other residents jealous as he appears to be the top contender for Chief Resident, Meredith and Derek make a decision that will change their lives forever, and Dr. Perkins presents Teddy with a very tempting proposition.

Personal and work pressures are adding up and have Meredith visibly on edge, Owen conducts formal interviews for the Chief Resident position, Cristina grows increasingly defiant, Alex and Lucy's undefined relationship gets tested, and Jackson suddenly backs out of the Webber's diabetes trial.

News of Meredith's dishonesty in the clinical trial comes to light, leading to unanticipated consequences for her and others; Cristina finds herself in a compromising situation, which forces her to decide between her career and her relationship; Owen posts his decision for Chief Resident, and Teddy makes a surprising choice regarding her love life -- and her future.

The fifth-year residents return for the first day of a year that will make or break their careers: Meredith faces the consequences of tampering with Derek's clinical trial and is terminated at the hospital; April tries to step up to the plate as Chief Resident in the wake of a giant sinkhole in the middle of Seattle; and Cristina and Owen are still at odds over their drastically different feelings for their unborn child.

News of Meredith and Derek's unsteady relationship raises a red flag for Zola's adoption counselor; Alex quickly realizes that he has become the outcast of the group after ratting out Meredith; and Cristina makes a tough decision regarding her unexpected pregnancy. Also, Chief Webber brings Henry in for a last minute surgery, alarming Teddy.

This is an historic episode that finally crosses a long-standing barrier.

The chief makes a decision that shocks everyone at Seattle Grace; Owen and Cristina attempt to find normalcy; April struggles in her new role; the 5th-year residents receive their first solo surgery assignments.

A stampede at a comic book convention leads to an influx of colorful characters in the ER; Mark continues to make life difficult for Jackson; Ben returns and realizes Bailey has moved on.

The residents try their hardest to impress surgical great Catherine Avery-who also happens to be Jackson's mother-when she arrives at Seattle Grace to perform a groundbreaking transplant surgery; Arizona and Alex find their hands tied with a confidentiality issue when a familiar patient comes into the ER; meanwhile, a love-struck Teddy throws a dinner party for the couples, and Bailey makes a decision regarding her love life

After being blackballed by most of the surgeons, Meredith uses Lexie to spark Derek's interest in her patient's rare brain tumor case and, in secret, gives guidance to April with Bailey's clinical trial; Callie's wish for Arizona and Mark to form a friendship comes to fruition and she realizes it's more irritating than helpful; Alex and Teddy research alternative surgeries for a very superficial patient; and Callie and Cristina struggle with a very difficult spinal surgery.

Owen stresses teamwork and moves his leadership role over to the baseball field when he signs the doctors up for a baseball league, pitting them against their biggest competition, Seattle Presbyterian; Lexie tries to hide her jealous rage when she sees Mark with a new woman, but her emotions get the better of her; Alex fights to keep Zola at Seattle Grace after it is suggested that she be moved to another hospital due to a conflict of interest with Meredith and Derek; and Richard scolds Meredith and Bailey for their feud

The doctors become nostalgic when George O'Malley's mother, Louise, returns to Seattle Grace for medical help after a botched surgery at a neighboring hospital; the residents are inspired by a medical miracle when they witness a harvested heart that continues to beat outside the body; a new pediatric fellow excites Arizona and makes Alex feel threatened; Jackson lets his suspicions about Mark and Lexie interfere with his work; and Henry and Teddy have their first marital fight when he expresses interest in pursuing medical school

Teddy puts her husband’s life in the hands of her peers when Henry is sent to the OR for surgery and she’s called away on another case; Meredith and Derek receive the long-awaited news about Zola; Callie and Jackson come under fire when their patient experiences post-surgery complications; and Meredith and Alex are involved in a life-threatening situation when they travel to a neighboring hospital to tend to a sick newborn, on Grey’s Anatomy

A severe car crash involving an entire family results in an all-hands-on situation in the ER, as the eldest daughter is left to make the toughest decision of her life. Meanwhile Teddy, still in the dark about Henry's death, calls upon Cristina to help with her patient in the O.R., and Lexie finds herself working alongside Mark's new girlfriend, Julia, during an eye surgery.

The doctors split into teams for a risky surgery involving conjoined twins; Bailey recruits Meredith to be a buffer between her and Ben when he puts pressure on moving their relationship to a more serious level; Richard teaches Alex a tough lesson in the OR; meanwhile Teddy questions Cristina about what exactly happened to Henry during his surgery.

Richard performs a monumental surgery in his career; Derek and Lexie attempt to work miracles for a patient with an inoperable tumor

As Meredith puts Zola to bed and falls asleep, she begins to wonder -- what if her mother had never had Alzheimer's and she'd had loving, supportive parents? The reverberations of a happy Meredith Grey change the world of Seattle Grace as we know it. What if she had never met Derek in that bar and he had never separated from Addison? What if Callie and Owen had become a couple long before she met Arizona? And what if Bailey never evolved from the meek intern she once was?

In the spirit of Valentine's Day, Meredith and Derek try to have a night to themselves when Lexie offers to watch Zola; Callie hands babysitting duties over to Mark so that she can surprise Arizona with a romantic evening; and Ben proves to Bailey that he knows her better than she thinks. Meanwhile, the ER fills with romantics, including a 10-year-old girl who has an allergic reaction to chocolates from her valentine and a man who is hit by a car while chasing down his frustrated girlfriend.

Amelia arrives at Seattle Grace to beg Derek to help with the gliosarcoma case; Cristina and Owen have heated arguments during marriage counseling; Alex realizes he needs to improve his people skills in order to be a good doctor.

As Adele's condition continues to deteriorate, Richard considers altering their living situation; an explosion at a local coffee shop results in a busy day in the ER for the doctors; Callie takes Meredith under her wing by helping her study for her boards; Lexie joins Arizona and Alex in peds, as they continue to care for intern Morgan's premature son; and when Jackson snaps at a patient, Mark encourages him to find ways to relieve his stress. Meanwhile, Cristina lets her suspicions get the best of her.

Derek encourages a hesitant Meredith to work with him again in neurology; Jackson's mother, Catherine Avery, returns to Seattle Grace with a urology fellow and develops an interest in Richard; and Cristina becomes increasingly suspicious of Owen's every move. Meanwhile, Alex tries to deny the fact that Morgan may be falling for him.

A lion breaks loose in Seattle, leaving a couple's lives and relationship at risk; Lexie overhears Mark's discussion about moving in with Julia; Teddy begins to take steps towards coming to terms with Henry's death; Callie grills Arizona on her past lovers; and Alex requests to be taken off Morgan's preemie case when she becomes too dependent on him. Meanwhile, Meredith tries to be a support for Cristina as the tension between her and Owen hits a boiling point.

A devastated Cristina presses Owen to confess the intimate details of his affair; Mark takes his new authority very seriously when he steps in as chief for the day and butts heads with Richard over a patient's liver transplant; and Callie deems Meredith ready for the boards, while the rest of the residents continue to stress about the exam. Meanwhile, Callie, Arizona and Bailey plan a much needed ladies night for Teddy.

The doctors work on a Jane Doe, who turns out to be the subject of a case that gained national interest; Cristina proves to be the highest in demand as the residents begin their interviews for post-residency positions at prospective hospitals; and Richard is faced with an unsettling realization when he visits Adele at Rose Ridge.

After eight years of practice, the residents head to San Francisco for their oral boards; sparks fly between Catherine and Richard when they bump into each other at the hotel; Bailey intervenes after Owen and Teddy get into a heated argument about their young car crash patient; and Mark tries to recruit Lexie for one of his cases. Meanwhile, Alex feels guilty for being away from the hospital when Tommy's health begins to fail.

The residents agonize over their oral boards, reliving every answer they gave during their exams; Arizona's close childhood friend comes to Seattle Grace for medical help; the doctors work on a patient who is missing one third of his skull; and Julia asks Mark to start a family with her. Meanwhile Catherine tells Richard that one of his residents has failed.

The residents determine their future as they make their final decisions regarding post residency positions; Mark admits to Derek that he is torn between his love for Lexie and the fact that Julia can give him everything he's ever wanted; Ben plans something extra special for Bailey, but she is preoccupied with her work; and Arizona encourages her childhood friend, Nick, to have surgery. Meanwhile a couple on their third honeymoon come to the hospital complaining of mysterious symptoms.

Faced with a life threatening situation, the doctors must fight to stay alive while trying to save the lives of their peers; Bailey and Ben make a decision regarding their relationship; and Teddy is presented with a tempting offer. Meanwhile, Richard plans a special dinner for the residents.

The doctors of Seattle Grace are faced with the aftermath of last season's plane crash. As they try to move on with their lives, they must learn to adapt to the changes, cope with their losses and move forward with their relationships and careers.

In this flashback episode, return to the site of the plane crash and watch as each doctor tries to cope with the heartache and injuries caused by the crash. Meanwhile, back at Seattle Grace, everyone struggles to find a bit of normalcy amidst the chaos.

The survivors from the crash are asked to make an almost impossible decision that will affect the rest of their lives. Meanwhile, tension grows between Jackson and April after they're forced to work together, and Alex tries to restrain himself with one of the interns.

Aware that Derek might never operate again, Meredith stops talking about the surgeries she's performing. Meanwhile, Richard calls on Dr. Catherine Avery to help him perform a complicated procedure, as things continue to heat up between Jackson and April; and Arizona's struggle to accept her fate forces Callie and Alex to face their guilt.

In this Meredith & Cristina-centric episode, the two friends continue to cope with life after the plane crash and their ever-growing responsibilities at their respective hospitals. As Meredith juggles taking care of Zola with a case that hits close to home, Cristina assists Dr. Thomas on a challenging heart surgery.

As the doctors continue with their lawsuit, they’re forced to confront the realities of their injuries. Meanwhile, Bailey tricks Arizona into helping her with a pediatric case, and Cristina tries to find normalcy in her new environment.

Cristina and Owen continue to figure out their relationship amidst the pending lawsuit; and Bailey argues with Ben over plans for their upcoming nuptials. Meanwhile, Callie recruits Jackson to help find a solution to Derek's hand, but he is preoccupied by a shocking situation with April.

The new batch of interns find themselves involved in all the drama at Seattle Grace: Meredith asks Heather to go above and beyond to help fix Derek's hand; Cristina starts a healthy competition between Stephanie and Leah, which inadvertently leads to a medical emergency for Cristina's patient; Alex sees Jo in a new light as they work to save a baby's life, and April teaches Shane a valuable lesson during "lumps and bumps" duty.

As the rest of the doctors prepare for Bailey's wedding, Richard helps her through a bout of pre-wedding jitters. Meanwhile, Lizzie butts heads with Meredith, and Callie and Jackson try to convince Derek to participate in a risky surgery that could fix his hand.

Bailey puts her wedding day on hold and continues her efforts to save Adele's life, Cristina and Owen remain undecided about their pending divorce, while Arizona and Callie try to get their spark back. Meanwhile, the hospital becomes inundated with a group of bikers after a horrible accident.

Meredith, Derek, Cristina and Arizona receive big news regarding the plane crash lawsuit, Richard avoids Catherine's romantic advances and Jackson takes on one of Mark Sloan's old patients. Meanwhile, Derek begins recovery on his hand.

The Seattle Grace doctors are on edge when a new medical professional enters the hospital; Arizona struggles with the emotional and physical pain of a phantom limb; and while battling pregnancy hormones, an overly-emotional Meredith is confronted with her worst fear.

As Derek and April work around the clock to find a solution for the hospital, Cristina struggles to respect the wishes of a family whose son is dying. Meanwhile, Arizona empathizes with a teenager who faces problems similar to her own.

Competition heats up as several of the doctors fight to become the new face of Seattle Grace; April brings in an emergency case, and Jackson and Alex work with a transgender teen couple. Meanwhile, the hospital implements new policies which test the patience of the staff.

As the hospital spirals closer to financial ruin, Owen must make some tough decisions, which includes foregoing an expensive surgery that could save the life of a child. Meanwhile, Alex and Jo work together to save the life of an infant, and April asks Jackson for dating advice.

As word of Seattle Grace's financial trouble spreads, Catherine encourages Jackson to move to Boston, and the interns fear they might lose their jobs. Meanwhile, the doctors meet with a potential investor in a last-ditch effort to save the hospital, and Alex impresses Jo while caring for a patient.

The discord and chaos created by the hospital's new management team causes one physician to question his future at Seattle Grace. Meanwhile, the doctors and the interns must juggle several transplant surgeries at once, each coming with its own set of obstacles.

As the hospital continues to make positive changes under the new management, the doctors begin to realize that owning a hospital comes with its own set of problems and responsibilities. Meanwhile, Meredith worries about the wellbeing of her unborn baby, Callie and Arizona try to get the spark back in their relationship, and Alex gives Jo‘s new boyfriend a run for his money.

A gas tanker explodes on a Seattle highway, causing multiple injuries, including paramedic Matthew. Meredith and Jo help a frantic mother whose child is suffering from a mysterious illness. Owen bonds with a young boy whose parents are in critical condition. Meanwhile true colors are revealed when Alex is forced to work with Jo's boyfriend on an ailing patient.

Upon receiving some unsettling news, Meredith and Derek take preventative steps for their children’s future; a group of Syrian doctors arrive at Grey Sloan Memorial Hospital for a crash course in basic surgical skills that they plan to apply in the field; and April decides to come clean to Matthew regarding the truth about her virginity. Meanwhile, multiple pre-op patients develop infections, causing one doctor to wonder if she is at fault.

Bailey finds herself at the center of a CDC investigation surrounding the death of several of her patients, as Jackson and the rest of the board members argue over how to address the crisis with the public. Meanwhile, Cristina teases Alex about his unspoken feelings for Jo, and Owen continues to take special care of Ethan as the condition of his parents remains uncertain.

The doctors reach out to Bailey but she continues to shut everyone out; after an incident with Ethan's grandmother, Owen fears the child could end up in foster care. A new craniofacial specialist arrives at Grey Sloan Memorial Hospital to work on a young patient. Meanwhile, a magician's assistant is rushed into the ER after a magic trick goes terribly wrong.

The doctors of Grey Sloan Memorial Hospital prepare for a super storm heading towards Seattle. Owen's desire to be a parent gets stronger as he becomes closer to Ethan. One wrong move puts the lives of Meredith and her baby in jeopardy. Meanwhile, Jo looks to Alex for help in a moment of crisis, and one doctor gets the shock of her life.

Grey Sloan Memorial Hospital enters crisis mode as the storm rages, resources become scarce and patients flood in by the busload. Meanwhile, one of the doctors fights for their life.

The Grey Sloan Memorial Hospital doctors are faced with the devastation left by the storm. A giant mudslide in Seattle injures a group of first responders and citizens, causing the already short handed ER to spring into action. Meanwhile, Meredith is faced with a tough decision that will affect the life of a loved one, Callie is rocked by the reality of Arizona’s infidelity, and Richard’s life is in extreme danger.

Callie makes a decision about her relationship; the doctors receive devastating news.

Derek and Meredith adjust to life at home with their newborn; Arizona tries to repair her marriage; Jackson and Owen clash over financial issues.

The doctors of Grey Sloan Memorial throw a fundraising gala which turns wildly competitive after Jackson makes a rash promise. Back at the hospital, Bailey’s patience is tested when she has to deal with several extremely difficult patients. Meanwhile, Shane and Stephanie handle an incredibly busy ER by themselves and Alex reveals an emotional secret to Jo.

Meredith struggles to balance her roles as a surgeon and a mother when she returns to work; Stephanie tries to impress Jackson's mother; Jo becomes overly involved with a patient.

Derek and Callie work on a brain mapping project, Richard encourages the interns to use his physical condition as a learning tool and after a discussion with Callie, Meredith considers continuing her mother’s research. Meanwhile, Shane continues to feel guilty about Heather’s death.

Costumed patients create a challenge for the doctors; Derek and Ben work on a new surgical technique; Richard asks a resident to perform his next surgery, angering Bailey.

A betrayal intensifies the issues between Cristina and Meredith; Matthew and April make a decision about their relationship; Bailey faces difficulties with Ben's return.

When an unexpected malpractice suit turns Callie's world upside down, her supportive father arrives and shares an interesting secret with her. Meanwhile, through flashbacks, we learn some surprising details about Callie and Arizona's marriage.

Ben worries that a casual conversation with Derek could potentially cause issues for Bailey, Cristina turns to Shane as tension grows with Meredith, and April's upcoming wedding makes for an uncomfortable situation between Jackson and Stephanie. Meanwhile, Meredith plans a Thanksgiving dinner at her house.

April’s sisters arrive to help celebrate April’s upcoming nuptials and quickly get on her nerves. Matthew and Jackson are forced to work together when they witness a terrible accident, Callie and Arizona work hard to reestablish their relationship and Cristina is pressured to live stream an upcoming surgery. Meanwhile, a familiar face returns to the hospital.

On the day of April's wedding, the Grey Sloan Memorial doctors are all preoccupied with their own drama. Meredith and Cristina continue to argue about their research and careers, Bailey comes clean to Ben about her feelings regarding him moving back to Seattle, and Shane puts himself in a risky situation. Meanwhile, Derek gets a phone call that will change his life.

The doctors are faced with the consequences of the events at April's wedding. Alex reacts to the news about his father. Callie and Arizona make a decision about their relationship.

After an anonymous complaint is issued by one of their own, the hospital implements a non-fraternizing policy causing the couples to panic. Meanwhile, Emma and Owen talk about the future, Cristina and Meredith enjoy a little girl time, and Richard enlists the residents to help research a rare cancer case.

Arizona has a bad day which escalates when she advises one of Callie's patients on a potential double amputation. Derek goes back on a promise to Callie, and Jo and Stephanie come across an abandoned baby outside the hospital. Meanwhile, the doctors deal with the repercussions of the non-fraternization rule, which include meetings with HR and one doctor's suspension.

It's Richard's birthday and Bailey invites him to scrub in on the case of a lifetime. Meredith hires a research assistant to help with her portal vein project. A scorned Callie gives Derek quite the shock. Meanwhile, Shane helps screen candidates for Cristina's clinical trial and meets a young expectant mother who needs his help.

Cristina imagines the two routes her life can take based on one decision she makes. Meanwhile one of the hospital’s patients decides whether or not to live.

The hospital gets inundated with flu infected patients, which causes the doctors to slowly fall ill one by one. Derek must fight off the sickness as he prepares to give a speech on brain mapping and the residents place bets on who will fall ill first. Meanwhile, a new doctor at the hospital gives Alex a glimpse into an alternate form of medical practice.

Cristina won't let herself get excited when she is nominated for a Harper Avery award; Alex thinks about making a change; Callie and Derek work with a machine that recognizes emotions.

Cristina enlists Meredith to help her prepare an acceptance speech for her possible Harper Avery win and while Owen offers to attend the ceremony with her, she insists on going alone. Meanwhile, Derek feels overwhelmed between his responsibilities at home and at the hospital. April and Jackson come to a disagreement on children and religion, and Callie and Arizona try to reconnect in their marriage.

Jackson is given the daunting task of delivering disappointing news to the doctors. Meanwhile, Derek's sister Amelia drops by for a surprise visit, Richard surprises Catherine in Boston and when Bailey gets frustrated by the slow pace of her research, she makes a risky decision.

Cristina considers her future at the hospital; Amelia and Derek collaborate on a tough surgery involving conjoined twins; Jo takes on too many cases at once; Stephanie stumbles on the truth about Bailey's case.

With Derek away, Meredith spends time with Amelia and finds out her true feelings about her time in Seattle. Bailey deals with the ramifications of her actions and Callie receives devastating news. Meanwhile, the residents panic after hearing that one of them will be fired

The doctors of Grey Sloan Memorial Hospital bid an emotional farewell to the beloved Cristina Yang. A possible act of terrorism rocks Seattle and causes chaos at the hospital. Meanwhile, Meredith makes a life changing decision and one doctor receives shocking news.

With Cristina gone, a new doctor, Maggie Pierce, making the rounds and Derek wanting to move to Washington DC, Meredith struggles to regain a sense of normalcy both at home and in the hospital. Meanwhile, Callie and Arizona come to a decision about surrogacy, Amelia overhears a big secret, Bailey realizes she will have to fight Alex for Cristina’s board seat and a freak accident causes two teenagers to be caught in a very compromising position.

Maggie tries to make a good impression but finds herself in unfortunate situations; Richard keeps hiding his secret.

Owen tries to get Callie to help Veterans Hospital patients with the robotic limb lab. Alex and Meredith's friendship makes Jo jealous. Alex and Bailey prepare to go in front of the board.

Secrets from Ellis Grey’s past come to light when Meredith watches old videos and reads through her mother’s journals. Meanwhile, Maggie rocks the hospital with an unexpected announcement; Alex gets new responsibilities and Callie focuses her attention on the Veterans’ project.

Callie and Arizona examine their marital problems and what's contributed to them. Meanwhile, Callie devotes herself to the veterans' project, Arizona strives to impress Dr. Herman, and Richard seeks guidance from Bailey.

Owen becomes invested in a patient when he realizes she may have served in the military, April’s mother pays her daughter a visit and bonds with Jackson, and Derek plans a family dinner. Meanwhile, a patient’s diagnosis causes Bailey to reconsider her own health issues and Dr. Herman drops a bombshell on Arizona

Information about Amelia's past emerges and causes problems for her at the hospital.

Maggie and Meredith disagree with Derek about the best way to approach a patient’s case, which leads to a bigger argument between the couple. Meanwhile Callie feels responsible when one of her veterans is pushed too far and one doctor’s routine procedure results in a devastating diagnosis.

As Derek prepares for his move to DC, Meredith keeps herself busy at the hospital. Meanwhile, Jackson and April deal with difficult news, and Arizona and Amelia discuss how to best approach Dr. Herman.

April stays optimistic as Arizona begins testing on her baby; Dr. Herman plans out a crash course in fetal surgery; and Owen and Callie encourage each other to get back into the dating scene. Meanwhile, Meredith, Maggie and Bailey use the 3D printer to gain a better understanding of their patient's tumor.

After several discussions with Dr. Herman, April and Jackson must face their situation head on and make a difficult decision regarding their unborn child. Catherine arrives in Seattle and bumps into Richard at the hospital. Meanwhile, Meredith tries to find someone to take care of the kids so she can visit Derek for the weekend, and Amelia shows Stephanie some tough love when they work together on a case

Maggie gets upset when Meredith dodges her questions about DC; Bailey and Ben become concerned about Ben’s brother after he is admitted to the hospital, and Dr. Herman starts to warm up to Arizona. Meanwhile, Richard feels manipulated by Catherine.

The hospital doctors become fascinated with Dr. Herman’s case when Amelia gives a lecture detailing the intricacies of the surgery. Arizona and Herman continue to bond over the amount of cases they are trying to complete before the big surgery. Meanwhile, Bailey brings them a case of a pregnant woman who is close to her heart.

In this Amelia-centric episode, Amelia engages in the surgery of a lifetime as a crowd of doctors look on from the gallery. With Stephanie by her side, she begins operating on Dr. Herman, but quickly realizes it's far more difficult than she anticipated. Meanwhile, Bailey becomes skeptical when Arizona takes on one of Herman’s cases.

An earthquake shakes the ground at Grey Sloan Memorial Hospital, trapping Maggie in an elevator and threatening Meredith’s long streak of successful surgeries. Meanwhile, Owen gives medical advice to a child over the phone and Ben confides in Jackson.

A patient's condition sparks a conversation between Richard and Maggie about Alzheimer's disease; April and Jackson struggle to return to their normal lives and Arizona is faced with the reality that Callie is moving on. Meanwhile, Meredith reveals her biggest fears about Derek.

Meredith, rattled by the latest events, tries to figure out what to do about Derek. Meanwhile, Owen is shocked when his mother is admitted to the hospital.

A school field trip to the hospital takes a dramatic turn when the kids witness two injured cops enter the emergency room. Meanwhile, Stephanie sets her eyes on one of the chaperons, Callie operates on the leg of the police captain and Amelia must face her feelings for Owen.

Upon realizing that Owen and Amelia have been seeing each other behind her back, Meredith comes down hard on her sister-in-law causing Amelia to rethink things. Meanwhile, Catherine springs into action when a man is brought into the hospital after his wife seeks revenge on his cheating ways.

A small plane crash in Seattle causes multiple casualties and brings back horrible memories for the doctors, especially Meredith and Arizona. Meanwhile, friction between Owen and Amelia makes for an uncomfortable working situation for Stephanie.

Derek witnesses a horrible car accident and springs into action to save lives.

Meredith and the staff feel the impact of losing one of their own; Jackson struggles with April's decision; Bailey and Ben argue about their future. Months after Derek's funeral, Amelia struggles with her emotions; April plans to return; and Derek's part in Meredith's life continues to grow.

The doctors of Grey Sloan Memorial Hospital are forced to put their emotions aside when a catastrophic event occurs.

As the doctors continue to tackle an unfathomable crisis, they are reminded of what is important and are brought closer together.

The doctors of Grey Sloan Memorial must contend with the COVID-19 pandemic; an unintentionally started fire has first responders from Station 19 bringing patients into the hospital for treatment.

Bailey finds herself in the middle of an argument with patients' families as they await news about their children who were injured in a fire; Winston surprises Maggie; Amelia and Link try to have some fun as new parents.