Intelligence investigates a doctor who gave his patients lethal doses of chemotherapy. Roman fights a wrongful shooting investigation.

The crossover starts on Chicago Fire S04E10 The Beating Heart (I) and Chicago Med S01E05 Malignant (II).

When Burgess and Lindsay respond to a call about a stabbing, the assailant turns out to be a kidnapping victim escaping her captor; Ruzek accuses Roman of having feelings for Burgess.

Responding to a call about a suspicious duffel bag at the Chicago Lakefront, Voight is horrified to discover that the bag contains the frigid and unmoving body of a newborn baby. Meanwhile, Voight is surprised to hear that his son is in town and Burgess and Roman grow closer.