A member of Firehouse 51 clings to life and takes a sudden turn for the worse as medical staffers race to give treatment. Meanwhile, Dr. Natalie Manning prepares for her pregnancy and members of Chicago P.D. probe the case of a woman pulled from a fire.

The crossover starts on Chicago Fire S04E10 The Beating Heart (I). It continues on Chicago P.D. S03E10 Now I'm God (III).

Dr. Rhodes and Dr. Choi clash over the final decision made by a dying patient. Meanwhile, a pending lawsuit against Dr. Halstead moves forward, and doctors race to save a patient with a misdiagnosed flesh-eating bacterial disease.

A teen patient with abdominal pain firmly refuses any drugs. Meanwhile, Dr. Halstead reconnects with his past when treating a patient; a pregnant woman does everything in her power not to deliver the child; and Dr. Rhodes tries to avoid family issues.

Dr. Rhodes begins a fellowship in cardiothoracic surgery, only to have problems with his new boss. Dr. Choi is the new chief resident. Dr. Charles approaches Sarah with an interesting opportunity that catches her off-guard. April faces her recently discovered illness.

A car accident that occurs at the Chicago Marathon leaves a victim in critical condition and tests the mettle of Dr. Halstead, April and her fourth-year medical resident brother Noah, who must perform a difficult procedure in the field. A mother brings in her 8-year-old girl experiencing a sudden hearing loss and Dr. Manning is left to tend to the case, which takes a complicated turn. Dr. Choi deals with Olga, a woman who is malnourished, prompting him to bring in Dr. Charles to help assess the case. Meanwhile, Goodwin takes measures to get her personal life in order.

Sharon Goodwin's childhood sweetheart arrives at the hospital, but finds himself in dire straits. To help get his financial footing, Dr. Halstead gets lured into a concierge doctor app idea. Meanwhile, a young woman with a heart infection is treated by Dr. Rhodes against Dr. Charles' advice and Reese's former patient, a sex trafficking victim, reaches out to her for help.

Dr. Halstead and Dr. Manning deal with two warring brothers who are brought together when one finds himself in desperate need of a kidney. Dr. Reese's former patient Danny comes to a crossroad. Dr. Rhodes and Dr. Latham treat a 16-year-old girl with a genetic condition in need of surgery, but whose overprotective mother disagrees with that course of action. A convict with unusual intentions puts himself in the hospital and Dr. Charles meddles in his daughter Robyn's personal life, much to her dismay. Meanwhile, Dr. Halstead and April make a discovery that complicates her treatment for TB.

Dr. Reese is contacted for help by a troubled teen in a psychiatric facility and Dr. Manning tries to help parents make a decision about their comatose daughter's surprise pregnancy. April begins to deal with repercussions from her personal life. Meanwhile, Dr. Choi and Dr. Rhodes work to save both a young girl from Ecuador who collapsed mid-flight, as well as her mother, who made great sacrifices for her daughter.

A suicide shakes the staff. Dr. Choi and Dr. Halstead face off over how to treat a patient with stroke symptoms. Family turmoil unfolds when a boy is treated after falling in a river. The importance of learning from mistakes is emphasized to Dr. Reese.

A hacker demanding a ransom payment shuts down the hospital computer system, forcing the doctors to diagnose patients without the aid of technology. A stressed Goodwin struggles to keep the hospital afloat when an unexpected visit from her ex-husband Bert and his new girlfriend make matters worse. Making use of his former navy experience, Dr. Choi and Noah have to locate a bullet inside a patient with a gunshot wound. Meanwhile, Sarah feels Dr. Charles may be trying to push her out and Robin's unusual behavior worries Dr. Rhodes.

Things get personal for Dr. Halstead when his unsupportive father is admitted to the hospital against his wishes. When treating Will's father, Dr. Rhodes reflects on his relationship with his dad. Dr. Charles gets involved when his daughter Robin's strange behavior continues to intensify and Dr. Choi struggles to help a teenage boy who is desperate to control his sexual urges. Dr. Manning feels the impact of being a working mother when a young boy is brought in for neglect. Meanwhile, Sarah teaches a group of high school students about the responsibilities of having a child by using fake baby dolls.

Dr. Rhodes fights to save a mother who's desperate to help her daughter beat cancer. Dr. Charles asks Sarah to conduct his daughter Robin's psych evaluation. When Will and Dr. Manning spend more time together at work, Nina goes to extreme measures to get Will's attention. Meanwhile, Dr. Choi puts pressure on Noah when a residency spot becomes available.

Dr. Rhodes challenges Dr. Charles and other hospital staff over the proper treatment for Robin. Dr. Manning seeks help from Det. Halstead when a sensitive case involving a young girl turns into a crime. Dr. Choi and April work together on a conflicting case. Meanwhile, Goodwin helps a friend in distress and, after eagerly awaiting, the doctors are surprised to learn who the new med resident is.

A new hotshot doctor arrives at Chicago Med causing competition for Dr. Rhodes, Dr. Halstead and Dr. Manning work together to diagnose a Syrian refugee without a medical record. When Robin is admitted back into the hospital for more complications, Dr. Reese takes a different approach to her treatment. Distracted from work because of Robin's worsening case, Dr. Charles is challenged by Goodwin and Noah hosts a graduation party that brings everyone together.

The doctors of Chicago Med take their opinions to the extreme as they try to bring justice to the perpetrator in the shooting of Dr. Charles. Dr. Halstead and Dr. Manning work on a heart-wrenching case that forces them to examine their own matters of the heart. Though Robin’s brain tumor was removed and she is discharged from the rehabilitation center, Dr. Rhodes remains on edge that her problems are not quite resolved. Meanwhile, Rhodes gets blindsided by his colleague Dr. Bekkar, Maggie sticks up for a patient and Dr. Choi and April try to navigate their new working relationship.

Dr. Manning goes to extremely measures to help a fearful pregnant woman whose baby is severely underdeveloped. April is angered by Dr. Choi when he uses their personal relationship as leverage to convince a patient of a risky procedure. As Dr. Rhodes attempts to balance his personal and professional life, it appears the stress of his current situation may have caused him to make a huge mistake.

When Goodwin receives financial complaints from the hospital board, she is forced to implement new guidelines that cause headaches for the doctors. Dr. Rhodes and Ava continue to compete in the operating room, while Dr. Charles and Dr. Reese are surprised when they treat a man who has a peculiar theory about his sickness. Dr. Manning and Dr. Cho can't figure out what is wrong with a young girl, leading them to look to a questionable source for answers.

Dr. Charles learns a troubling fact about the man who shot him. Dr. Rhodes and Dr. Bekker come to an agreement during a complicated surgery. Will and Natalie are trapped by legal ethics when an unfaithful husband refuses to tell his wife about his inconclusive Zika test. Meanwhile, April and Noah discover working together isn't always easy while Goodwin continues to argue with the board over hospital costs after an avoidable patient death.

When a young woman with HIV symptoms and no insurance refuses to take the test, Goodwin and Dr. Choi attempt to treat her without taking a toll on the hospital's resources. Natalie and Will try to diagnose a young girl with increasing paralysis. Noah deals with his first death as a resident and takes it upon himself to inform the family. Sarah continues to avoid work as her fear over the hospital's security increases.

Ethan attempts to diagnose a man with no symptoms while Sarah's paranoia goes to the extreme when she uses pepper spray on an aggressive patient. Will treats a young couple willing to sacrifice anything in order to have a baby. Meanwhile, Natalie must inform a woman that she was sterilized as a young girl without knowledge, and Goodwin and Maggie devise a way to persuade paramedics to bring in more patients.

After witnessing a drive-by shooting and hitting her head, Dr. Manning struggles with the aftermath of a head injury. Complicating matters, she and Dr. Halstead deal with a teenage patient and her overbearing older husband, who might not be looking out for his young wife's best interests. Dr. Rhodes finds himself in a unique situation when he learns alarming information about the woman he went on a date with. Maggie is surprised to discover some unexpected things about the man she has been seeing. Dr. Charles is frustrated when Dr. Reese disobeys his orders and puts herself at risk.

After a neighbor is stabbed, Dr. Choi enlists the help of April to figure out who is the real cause of the incident. Dr. Bekker and Dr. Rhodes expertise is put to the test when Noah misdiagnoses a patient. Dr. Charles is put in an uncomfortable position when Dr. Reese's estranged father comes to him as a patient without her knowledge. Meanwhile, Dr. Manning rushes to save a baby with whooping cough.

Dr. Halstead and Dr. Manning are at odds over the care of a vegetative man; Dr. Rhodes goes behind Dr. Bekker's back to get his patient at the top of the transplant list; a woman in the waiting room falls asleep and won't wake up.

After a baby is abducted from Med, Goodwin enlists the help of Dr. Charles and Dr. Reese to find the suspect. Due to the lockdown, Dr. Rhodes must figure out a way to get into the operating room to help perform open-heart surgery. Dr. Manning and Dr. Halstead disagree on the right treatment for a patient.

After taking the lead on a surgery, Dr. Bekker feels the heat after something goes wrong. Dr. Manning and Dr. Charles are faced with a tough decision concerning the gender of a 9-year-old girl. April and Dr. Reese rush to find the son of a dying patient. Goodwin's godson is admitted to the hospital.

After a 10-year-old boy is admitted to the hospital, Dr. Manning and Dr. Halstead disagree on how to best handle the boy's parents. Dr. Rhodes rushes to fix a heart that will be given to Dr. Reese's estranged father.

Bekker takes drastic action to keep Rhodes from leaving Med for good. Meanwhile, Halstead questions Manning's feelings about their upcoming wedding, Ethan receives shocking news about his sister, and Dr. Charles mourns a loss.

A power outage at Med puts multiple patients at risk and tests the skills of the staff and their enthusiastic med students; Natalie returns following her traumatic brain injury; Ethan and April wonder if a family is in their future.

Dr. Choi and Dr. Marcel don't see eye-to-eye over the treatment of a patient's chronic pain and rumors start to circulate about Maggie. Dr. Manning works to help a young boy, but her treatment suggestions are challenged by the parents who believe in only using holistic remedies.

Dr. Manning's actions with a recent patient lead to serious repercussions. April and Noah disagree over a patient who is injured after a beating. Dr. Charles is visited by a childhood friend with a surprising revelation.

Maggie gets unsettling news about a new friend and breaks protocol to support him. One of the doctors from the Med family is rushed into emergency surgery after a violent assault. A social media influencer lets his users vote on medical advice, forcing Dr. Charles to make a decision.

Dr. Halstead's world is thrown into turmoil when a former patient resurfaces. April has a secret she considers confessing to Ethan. Dr. Charles tries to maintain his focus during a difficult time.

After a major accident at O'Hare, the E.D. is concerned one of their own is in mortal danger. Will's proposal for a safe injection site goes to the board for consideration. Natalie and Goodwin become concerned for Gwen.

Two brothers in critical condition are rushed into the hospital by their parents, leaving Dr. Choi, April and Dr. Charles to tend to their care and left to piece together what actually transpired. Dr. Manning becomes suspicious of a new mother entering the E.D. Dr. Halstead’s tireless activities at the safe injection site start to take a toll on his work.

Dr. Charles and Dr. Manning treat a patient who is fully invested in pretending to be someone other than himself. Noah begins to doubt his abilities as a doctor. Dr. Marcel and Dr. Choi are faced with a tough ethical decision. Dr. Halstead puts his faith in an addict.

Dr. Halstead finds continued success in his trial. Dr. Charles' daughter, Anna, receives life-changing news. Noah finds himself in a situation not even April can fix.

Halstead relies on Marcel and Med's newly donated OR 2.0 to save his patient. Charles helps an elderly, confused patient who's mourning the loss of his high school sweetheart. As their wedding day approaches, Choi and April run into some roadblocks.