Chicago Fire Season 3 Episode 21
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).