Law & Order: Special Victims Unit: Season 15, Episode 4

Internal Affairs

Officer Michael Groves 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 enlists the help of the SVU to investigate, and plants Brian Cassidy as an undercover. But one crooked cop goes to great lengths to keep things as they are, and the squad realizes too late that they put Cassidy in grave danger.