Sometimes truth is stranger and more entertaining than fiction. Such is the case with “Black Mass,” a film based on the true story surrounding the unholy alliance between an FBI agent and Boston gangster James “Whitey” Bulger.

Johnny Depp’s portrayal of Bulger may well be the pivotal role of his career. At the very least, it’s transformative. I predict, when Academy Award time comes, Oscar-level attention. Given the wonders of make-up and Depp’s ability to channel speech, mannerisms, and a cold-blooded gaze, the character on the screen bears no resemblance to that roguish pirate that Depp has so artfully perfected.

With a strong script and impeccable casting, “Black Mass” pulls you in to the underside of high-level crime. This is not a safe picture. Brutality constitutes part of the survival code. I lost count of the cold-blooding killings – bullet to the back of the head of Bulger’s unsuspecting victims and bloody beatings. Nobody is safe from his wrath: former friends, the Italian mafia, and former employees all meet their end because they cross Bulger.

If Bulger doesn’t commit the deed himself, his henchmen do while he stands by and observes. Bulger seems unstoppable, rising quickly from small-time crime to the big leagues. Given the crack-down on Boston syndicates, how is that possible? Until a change in FBI administration, nobody stops to ask.

When they do, the FBI agent at the center of it all is John Connolly (Joel Edgerton), a man who rose in the FBI ranks from a scrappy life in a hard, south Boston neighborhood. Bulger and Connolly share a past, and in a manner of speaking, they’re thick as thieves. So, of course, Connolly knows Bulger’s brother Billy (Benedict Cumberbatch), the one person who gives the alliance credibility. Billy’s as respectable as his brother is flawed. He’s an educated, well-liked politician in the Massachusetts  senate, and Billy is smart enough to stay squeaky clean.

When Connolly first approaches Bulger about helping the FBI bring down the Italian mafia, he has good intentions. As time passes Bulger maneuvers the partnership and sucks Connolly into a dark hole of deceit and double-dealing. While the FBI focuses on what it believes are substantial leads from Bulger, Bulger runs amuck.

Agent Fred Wyshak (Corey Stoll) will connect the dots, along with operatives Fitzpatrick (Adam Scott) and McGuire (Kevin Bacon). The film’s last scenes disclose the outcome of it all. Connolly’s forty-year sentence assures that he will die in prison. Bulger will disappear into a California mist for many years, but there is another chapter.

Rest assured; ultimately crime does not pay.

Rated R for brutal violence, language throughout, some sexual references and brief drug use.

Marilyn Robitaille has been writing film reviews for the Empire-Tribune since 1999.