In the 1970s, Irish crime boss Whitey Bulger collaborated with the FBI to take down the Italian mob. The story of how he became the most feared and powerful gangster in South Boston, who could evade the law and walk the streets toting guns, is the subject of the upcoming film Black Mass.

Johnny Depp stars as the Irish crime lord, topping the billing with other big Hollywood names: Benedict Cumberpatch, Kevin Bacon, Joel Edgerton, and Dakota Johnson.

The new trailer for the film reveals Depp's transformation into Bulger as he dishes out some life lessons to his six-year-old son.

"It's not what you do; it's when and where you do it. And who you do it to or with ... If nobody sees it, it didn't happen."

The rest of the trailer teases some good old fun the only way a crime boss knows how. Double-crossing the cops, beating up his enemies, pointing guns in broad daylight, and even taking a pleasant walk out in his neighborhood where a nice old lady asks him when he got out of Alcatraz. Ten years ago, he says to her very kindly.

"Well, it's good to have you back," she tells Bulger.

Depp is already upping the hype for the movie for his portrayal of Bulger. From poor parenting advice to the moments of gore and violence, the film promises to deliver some action-packed thrills along with moments of humor and levity.

Glimpses of the all-star cast are also seen in the trailer about the most dangerous man in Boston.

The film, directed by Scott Cooper, will be out in theatres on Sept. 18. Cooper's other film hits include Crazy Heart (2009) and Austin Powers: The Spy Who Shagged Me (1999).

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