S3, E13: Lindsay (Sophia Bush) goes undercover in an effort to track down a rogue police officer targeting women leaving a local casino. When Detective Martin Watts (guest star Erik Jensen), who oversees all cases out of the casino, gets word of the investigation he becomes involved much to Voight's (Jason Beghe) dismay. After recent events, Burgess (Marina Squerciati) sets plans in motion to transfer Districts pending Platt's (Amy Morton) approval, and Mouse (guest star Samuel Hunt) attempts to lift Ruzek's (Patrick Flueger) spirits by offering to set him up with a friend. Meanwhile, Antonio (Jon Seda) volunteers to take Roman's (Brian Geraghty) place in the upcoming boxing match against Jimmy (guest star Steven R. McQueen) from Firehouse 51.