Platt is sent to the hospital after a vicious attack outside her father's house. Mouch is questioned and past threats against her are revisited while the team investigates. A gruesome discovery inside the father's home ups the ante in the case.

Halstead's partying with Camila unintentionally puts him in the middle of a drug-related homicide. He's forced to choose between loyalty to his unit and his girl. Meanwhile, Voight finally discovers the mole in his unit.

After discovering the true cause of the high-rise fire, Intelligence races to find the man responsible. And for Halstead, it’s personal.

The crossover starts on Chicago Fire S07E02 Going to War (I) and Chicago Med S04E02 When to Let Go (II).

In the midst of a momentous rainstorm, Intelligence lends support to Officer Cook when she and her partner disagree about an investigation.