Bob Ruzek is the first to arrive on the scene of a double murder. Intelligence arrives to take over the investigation and tensions arise as Bob needs to hand over the case to his son and Voight. Lindsay's new gig has her planning a trip to Bolivia for an undercover investigation that could be for an extended amount of time. Burgess and Roman realize they need to put past events behind them so it doesn't jeopardize them going forward.

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 Lindsay is tipped off about a grieving father looking to avenge his daughter's death, Olinsky goes undercover as a hitman-for-hire. With Gang Intelligence lacking enough evidence to arrest the original gangbanger in question, the team works to reinvestigate the case. Meanwhile, Ruzek comes back after finishing his undercover assignment only to have Voight knock him down to patrol duty.