On the other side (The Departed) is a 2006 American crime film directed by Martin Scorsese written by William Monahan. The film is based on the 2002 Hong Kong film "Infernal Affairs", with its script being revised. The film premiered on September 26, 2006.
In South Boston, the state police are waging war on Irish-American organized crime. Young undercover cop Billy Costigan (Leonardo DiCaprio) is assigned to infiltrate the mafia syndicate led by gangster boss Frank Costello (Jack Nicholson).
While Billy quickly gains Costello's trust, Colin Sullivan (Matt Damon) – a hardened young criminal tasked with infiltrating the state police as a syndicate informant – rises to a management position in the Special Investigations Unit.
Each of them delves deep into their second lives, extracting information about the plans and counter-plans of the operations they infiltrate. But when it becomes clear to both the mafia and the police that there is a rat in their midst, Billy and Colin find themselves in danger of being exposed by the enemy, so each must rush to reveal the other's identity in order to save themselves...
