A frustrated Severide, turns to an unlikely ally to resolve his current dilemma. Casey begins to find satisfaction in his personal life, while Mills and Dawson face personal challenges. Meanwhile, the squad is called to the scene of a harrowing apartment building collapse.

Events force Lieutenant Casey to team up with the Intelligence Unit, now run by Voight, who doesn’t appear to have changed his crooked ways after his stint in prison. Shay's excitement at the prospect of becoming a parent grows, while Mills and Dawson face some personal challenges. Meanwhile, the house comes together to support the opening of Molly's.

Lt. Casey and Dawson volunteer to help at a charity run at Chicago Medical when a massive explosion sends Chicago into chaos. With one of their own missing in the blast, the firehouse is tested like never before.

The crossover continues on Chicago P.D. S01E12 8:30 PM (II)

Severide lobbies Chief Boden for a favor for Scott Rice, an old friend needing a second chance with the CFD, but Casey and Otis have their doubts. Elsewhere, Mills works to regain his active squad status while Brett and Dawson decide they need a big night out.

The Chicago fire team works seamlessly with Chicago Med personnel to help aid victims of a deadly gas leak, but things quickly take a turn for the worse when the hospital is suddenly forced into quarantine.

An apartment fire connected to a case of rape and attempted murder resembles an unsolved case in New York, so Sgt. Benson of Special Victims Unit comes to Chicago to help Intelligence with the investigation.

The crossover continues on Chicago P.D. S02E20 The Number of Rats (II) and Law & Order: Special Victims Unit S16E20 Daydream Believer (III).

Firehouse 51 unites to help a young boy in tragic circumstances. A high-powered political consultant helps Casey navigate a potential scandal. Cruz makes a mistake that nearly costs him his life.