Black Mass (2015)

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The true story of Whitey Bulger, the brother of a state senator and the most infamous violent criminal in the history of South Boston, who became an FBI informant to take down a Mafia family invading his turf.
Director: Scott Cooper
Writers: Mark Mallouk (screenplay), Jez Butterworth (screenplay) | 2 more credits »

Stars: Johnny Depp, Benedict Cumberbatch, Dakota Johnson | 

In 1975, James "Whitey" Bulger, leader of the Irish-American Winter Hill Gang, controls most organized crime within South Boston, along with his right-hand man Stephen Flemmi, newcomer Kevin Weeks, and callous hitman Johnny Martorano. Bulger lives with common-law wife Lindsey Cyr and their young son.

Bulger's supremacy is challenged by the North end Angiulo Brothers, a rival gang, part of the New England Mafia family. FBI agent John Connolly returns to the area; he grew up in South Boston as a friend of Whitey and his brother William "Billy" Bulger, the Massachusetts State Senate President. Connolly tries infiltrating the Angiulo Brothers, and attempts to get Whitey to work with the FBI. Although Whitey hates the idea of being a rat, he understands the protections he would have for himself, his gang, and his family. When the Angiulo Brothers murder a Winter Hill member, Whitey becomes an informant.

Although Connolly is supported by his co-worker John Morris, their boss, Charles McGuire, is suspicious. Whitey increasingly exploits the FBI informant relationship, using Connolly's "protection" as a cover for his crimes. Connolly demands information on the Angiulos' racketeering locations. Finally, Whitey gets pictures of the rival gang's hideouts, allowing the FBI to wiretap the Angiulos. The FBI arrests them, thus eliminating underground opposition to Whitey's power. Connolly, blinded by his past, grows closer to Whitey and the gang, even inviting them to his house for a cookout. His wife, Marianne, sees negative changes in her husband as his agent-informant relationship with Whitey grows.