Mayor Tom Kane finds out he has a serious medical condition and tries to focus on the upcoming gubernatorial primary.
The team searches for a missing child in what turns out to be a very complicated case; Burgess and Ruzek are in for a shock when someone from Makayla's past comes forward.
On Colvin's orders, Wysocki and Evers try to track down a drug dealer. As the detectives chase their leads, an unexpectedly elaborate case unfolds.
The record-breaking summer heat and the likelihood of blackouts send the Chicago Police Department into the streets in full force to temper the city's escalating violence. Alongside her new driver, Superintendent Teresa Colvin finds herself back in the field while Detectives Wysocki and Evers take over an emotional case in which a son witnessed his father's fatal shooting.
FBI Division Chief Cuyler (Adam Arkin) interferes with Wysocki and Evers' investigation of an international drug dealer; Liam feels vulnerable while visiting grieving families.