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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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

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.