"The Departed" is set in South Boston, where the state police force is waging war on organized crime. Young undercover cop Billy Costigan (Leonardo DiCaprio) is assigned toinfiltrate1 the mob syndicate run by gangland chief Costello (Jack Nicholson). While Billy is quickly gaining Costello's confidence, Colin Sullivan (Matt Damon), a hardened young criminal who has infiltrated2 the police department as an informer for the syndicate, is rising to a position of power in the Special Investigation3 Unit.
Each man becomes deeply consumed by his double life, gathering4 information about the plans and counter-plans of the operations he has penetrated5. But when it becomes clear to both the gangsters6 and the police that there's a mole8 in their midst, Billy and Colin are suddenly in danger of being caught and exposed to the enemy – and each must race to uncover the identity of the other man in time to save himself.
Legendary9 director Martin Scorsese takes the helm for this tale of questionable10 loyalties and inspired by the wildly popular 2002 Hong Kong crime film Infernal Affairs. As the police force attempts to reign11 in the increasingly powerful Irish mafia, authorities are faced with the prospect12 of sending in an undercover agent or seeing their already frail13 grip on the criminal underworld slip even further.
Billy Costigan (Leonardo DiCaprio) is a young cop looking to make a name for himself in the world of law enforcement. Collin Sullivan (Matt Damon) is a street-smart criminal who has successfully infiltrated the police department with the sole intention of reporting their every move to ruthless syndicate head Frank Costello (Jack Nicholson).
When Costigan is assigned the task of working his way into Costello's tightly guarded inner circle, Sullivan is faced with the responsibility of rooting out the informer before things get out of hand. With the stakes constantly rising and time quickly running out for the undercover cop and his criminal counterpart, each man must work feverishly14 to reveal his counterpart before his identity is exposed by the other.