Young undercover cop Billy Costigan infiltrates Irish-American organized crime, while a hardened criminal, Colin Sullivan, secretly works as an informer for the syndicate within the state police. Both men navigate their double lives, gathering information, but their identities are threatened when it becomes clear there's a mole.

The Departed
In the gritty streets of South Boston, a cat-and-mouse game ensues between a skilled undercover cop and a rogue police mole, each trying to outwit the other and uncover the truth about their identities.