The Departed

To take down South Boston's Irish Mafia, the police send in one of their own to infiltrate the underworld, not realizing the syndicate has done likewise in Martin Scorsese's multiple Oscar-winning crime thriller. While an undercover cop (Leonardo DiCaprio) curries favor with the mob kingpin (Jack Nicholson), a career criminal (Matt Damon) rises through the police ranks. But both sides soon discover there's a mole among them.