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 Number of Rats (2) aired on Chicago P.D., S2E20. Daydream Believer (3) aired on Law & Order: Special Victims Unit, S16E20.)