The grand opening of Chicago Med's emergency department is interrupted by victims of an elevated train crash, pushing the staff to their limits.

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).

Sharon Goodwin puts her job on the line for a patient in need of a lifesaving bone-marrow transplant. Meanwhile, April cares for a homeless man, Dr. Manning's parents arrive, and a couple are injured during their first date by a hit-and-run driver.

A husband makes a request following his wife's death; Dr. Charles tries to reason with a patient who wants to remove his own arm from his body; a child arrives at the hospital after swallowing magnets; Sarah has last-minute thoughts about her residency.

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.

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.

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 and nurses of Chicago Med find themselves on high alert when an overflow of patients are rushed into the doors following a terrifying apartment complex blaze. Dr. Rhodes fights to save the life of one of Chicago Fire's own, while Dr. Halstead and his brother Jay struggle with their own personal battle.

The crossover starts on Chicago Fire S07E02 Going to War (I). It continues on Chicago P.D. S06E02 Endings (III).

When a sick boy is brought in, Ethan is faced with a tough decision that quickly escalates into a complicated and dangerous situation. Connor and Maggie are put to the test, while Natalie and Ethan aren't sure what to make of Elsa, the new third year medical student.

Dr. Halstead gets an unplanned visit from the CPD while Ethan is skeptical of a woman who is experiencing chronic pain. Natalie tends to a cancer patient whose brother has strong feelings on why he is refusing to lend his assistance

When things become complicated, Will is forced to lie to Natalie. Ethan and April find out some compromising information about Emily's boyfriend and Ava is unsure of what to do with a patient who is refusing treatment.

Dr. Manning and Dr. Halstead become skeptical of a patient's injuries when the victim of a car accident is brought into the hospital. Ethan and April have a difficult time understanding Emily's attachment to her boyfriend despite recent developments. Will and Natalie brace for their joint bachelor/bachelorette party.

The hospital is forced to evacuate when a toxic chemical is brought into the E.D., leaving patients and the staff in grave danger. Stuck in an elevator, Dr. Charles and Dr. Manning are forced to take drastic measures with a pregnant woman. Goodwin is tasked with making difficult choices and Dr. Rhodes discovers a secret that Dr. Bekker has been holding from him.

Will and Natalie prepare for their big day, but an unsuspecting Will soon finds himself sidetracked. Dr. Charles disagrees with Goodwin on how to best handle a patient's treatment while Dr. Choi and April are on their own when a pregnant woman delivers. Dr. Rhodes finds himself operating on a patient that is of great importance to Det. Halstead.

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.

The crossover starts on Chicago Fire S08E04 Infection (I). It continues on Chicago PD S07E04 Infection, Part III (III).

A convicted murderer’s escape hits close to home when several members of the team find themselves in danger. Dr. Charles and Dr. Halstead continue to clash over patient treatment plans. Dr. Choi and April discover the truth about a patient’s scam. Maggie finally receives some good news.