Good remake.

Rating: 10/10 (1 July 2016)

As a child, Colin Sullivan (Damon) had been introduced to organized crime by Irish-American mobster Frank Costello (Nicholson) in the Irish neighborhood of South Boston. Over the years, Costello grooms him to become a mole inside the Massachusetts State Police, until Sullivan is accepted into the Special Investigations Unit, which focuses on organized crime.
Before graduating from the police academy, Billy Costigan (DiCaprio) is recruited by Captain Queenan (Sheen) and Staff Sergeant Dignam (Wahlberg) to go undercover, as his family ties to organized crime make him a perfect infiltrator. He drops out of the academy and does time in prison on a fake assault charge to increase his credibility.
Each man infiltrates his respective organization, and Sullivan begins a romance with police psychiatrist Madolyn Madden (Farmiga). Costigan is seeing her under the terms of his probation, and they begin a relationship, too. After Costello escapes a sting operation, each mole becomes aware of the other's existence. Sullivan is told to find the "rat" and asks Costello for information to identify the informer.