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.
After four years without a lead, the team are called in to reopen the case of a young woman who vanished from her home. After numerous searches on an unidentified print found on her door, Vivian finally gets a match.