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).

Nurse Lockwood gets arrested when she takes a stand. Meanwhile, Dr. Halstead deals with a pending lawsuit against him; a baby's injuries come into question; Dr. Charles faces personal issues; and suspicions rise about a patient who was hit by a car.

An erratic patient arrives, claiming that his heart is pounding inside his head as he takes drastic measures to stop it. Also, Dr. Manning helps a boy with a broken wrist, but she suspects deeper issues exist; Dr. Rhodes impresses with his skills; and Will receives news about a lawsuit.

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).

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.

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).

In the aftermath of Halstead's apartment fire, Marcel, Choi and Archer work together to try to save the survivors. Charles and Med's new fellow, Cuevas, help a paranoid patient.

When a subway train goes off the tracks, Marcel volunteers to help the victims. Taylor and Halstead must decide if they’re willing to risk their jobs to save a patient. Asher and Archer clash over a pregnant patient.