The Number of Rats is the twentieth episode of the second season and the 35th overall episode of Chicago P.D. This episode is part two of a three-part crossover event between Chicago Fire (We Called Her Jellybean), Chicago P.D. (The Number of Rats) and Law & Order: Special Victims Unit (Daydream Believer).
Olivia Benson (Law & Order: Special Victims Unit) has come to Chicago to help Voight and Intelligence with a rape/murder case that is frighteningly similar to a case from New York a decade ago. She calls in Fin and Amaro to assist.
- Jason Beghe as Sergeant Hank Voight
- Jon Seda as Detective Antonio Dawson
- Sophia Bush as Detective Erin Lindsay
- Jesse Lee Soffer as Detective Jay Halstead
- Patrick John Flueger as Officer Adam Ruzek
- Marina Squerciati as Officer Kim Burgess
- LaRoyce Hawkins as Officer Kevin Atwater
- Amy Morton as Desk Sergeant Trudy Platt
- Brian Geraghty as Officer Sean Roman
- Elias Koteas as Detective Alvin Olinsky
- Mariska Hargitay as Olivia Benson
- Danny Pino as Nick Amaro
- Ice-T as Odafin Tutuola
- Peter Scanavino as Dominick Carisi, Jr.
- Nick Gehlfuss as Will Halstead
- Jesse Spencer as Matthew Casey
- Eamonn Walker as Wallace Boden
- Rachel Melius as Charlotte Reegan
- Laura Lapidus as Janine
- Jeff Parker as Dr. Smith
- Tiffany Bedwell as Victoria Lewyn
- Adrian Bond as Forensic Photographer
- Alyse Dionne as Lisa Hoffman
Notes and Trivia
- This episode includes a Law & Order-style introduction.