Dr. Choi treats a teen mother who abandoned her newborn baby in an alley, as the staffers must make difficult decisions about the teen's future. Also, a hypochondriac with chest pains is treated, as is a patient suffering from possible dementia.

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.

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.

April finds herself in a dangerous situation and Natalie gets an update on Will. Dr. Rhodes gears up for a gala honoring his hybrid O.R. and tries to convince Dr. Bekker to join 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).

Will and Stevie get stuck in the middle of a marital face-off. Dr. Blake's entire surgical team mysteriously collapses during a liver transplant. Charles encourages Ethan to reconcile with his father.

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.