S15, E4: Officer Michael Groves (guest star Marc Menchaca) ends up in a psych ward after turning on his old squad – he accuses the 12th precinct of cooking the books and making rape allegations disappear. Internal Affairs Lt. Tucker (guest star Robert John Burke) enlists the help of the SVU to investigate, and plants Brian Cassidy (Dean Winters) as an undercover. But one crooked cop (guest star David Conrad) goes to great lengths to keep things as they are, and the squad realizes too late that they put Cassidy in grave danger.