An apartment fire linked to a case of rape and attempted murder calls for members of the CPD to team with the Special Victims Unit, which had a similar unresolved case that has eluded them for more than 10 years. This prompts Sgt. Benson to come in f... (more)rom New York to assist with the investigation in which she is all too familiar. Meanwhile, doubts among the squad towards one of their own causes Severide to lay down the law and Dawson puts her life on the line during a call. (The Number of Rats (2) aired on Chicago P.D., season 2, episode 20. Daydream Believer (3) aired on Law & Order: Special Victims Unit, season 16, episode 20.)