The Departed (1966)

The Departed in the 1960s

South Boston cop Billy Costigan goes under cover to infiltrate the organization of gangland chief Frank Costello. As Billy gains the mobster's trust, a career criminal named Colin Sullivan infiltrates the police department and reports on its activities to his syndicate bosses. When both organizations learn they have a mole in their midst, Billy and Colin must figure out each other's identities to save their own lives.