Rat tales 

Movies about gangsters have long been irresistible to both the storytellers and the audience, and I think the reason they remain so eternally compelling is that we viewers are allowed to have our cake and then chase it with a $7 soda. We get to live vicariously through morally bankrupt men – and they are almost always men – doing things we might dream of only in our darkest moments, but we're also able to bask smugly in the inevitable reckoning when it's time for third-act justice.

Within all this bad behavior, though, lies a sort of honor that's traditionally found whenever people operate under a code of conduct, however skewed it may be. A bullet to the back of the head, for example, is acceptable, even expected. Tattling, however, crosses the line.

"I am not a rat" are actually among the first words spoken in "Black Mass," a violent, absorbing film about notorious Boston gangster James "Whitey" Bulger and his shocking quid-pro-quo relationship with the FBI that went unchecked for decades. The story is framed in flashback, as a few of Bulger's former associates sing to the Feds once they're finally arrested. We initially meet Bulger in 1975, and as played by Johnny Depp with a receding hairline, a dead tooth, and the most terrifying blue contact lenses in cinema history, Bulger is a career criminal making a living in clannish South Boston. His Winter Hill Gang seems to have an uneasy truce with "the goddamn dagos in the North End," but when an odd opportunity arises to neutralize the Boston Mafia, Bulger jumps at it.

"There's informin', and there's informin'," Bulger explains to right-hand man Steve Flemmi (the underrated Rory Cochrane) of his decision to enter into an alliance with ambitious FBI agent John Connolly (Joel Edgerton, "The Gift"), an arrangement further justified by the Southie-born Connolly's childhood friendship with Bulger's upstanding brother Billy (Benedict Cumberbatch), now an influential state senator. Connolly uses Bulger's street knowledge to dismantle the local Mob, looking the other way while his star informant fills this new power vacuum and savagely cements his standing atop the Boston underworld. It doesn't go entirely unnoticed by Connolly's colleagues, played by ringers like Kevin Bacon and Adam Scott, that Bulger appears to be getting a pass even as the bodies start piling up, but Bulger's sway at the FBI, financial and otherwise, didn't stop at Connolly... and it couldn't last forever.

All the review quotes are touting "Black Mass" as a return to form for Depp, and it's true that sinking his teeth into such a meaty lowlife elicits a spark not seen since he played another noted gangster, John Dillinger, in 2009's "Public Enemies." Depp's disciplined performance here is both chilling and somewhat chilly, as we don't really delve deep enough to learn what fueled Bulger's legendary sociopathy besides greed and a vicious instinct for survival. Depp's measured intensity is nicely balanced by the clownish swagger of Edgerton's Connolly, obviously in over his head as he tries to keep track of his lies. Cochrane is fantastic as the weary Flemmi, leading a wicked supporting cast that includes Jesse Plemons ("Friday Night Lights") and W. Earl Brown ("Deadwood") as Bulger's goons, as well as the scene-stealing Peter Sarsgaard as a coked-up hood.

Dakota Johnson, Juno Temple, and especially Julianne Nicholson ("Boardwalk Empire") as Connolly's skeptical wife all make impressions as the women who threw in with these lawless men. It certainly doesn't hurt that director Scott Cooper is in charge, having proved himself a friend to actors with films like 2009's Oscar-winning "Crazy Heart" and 2013's "Out of the Furnace." Now, wonky timelines and clearly speculative scenes make it necessary to mention that while "Black Mass" is based on a riveting nonfiction book by former Boston Globe reporters Dick Lehr and Gerard O'Neill, parts of the film are Hollywood supposition. (Documentary-wise, check out Joe Berlinger's excellent "Whitey.") Fortunately, this in no way detracts from any appreciation of the finished product, a worthy addition to the gangster-movie canon with a stranger-than-fiction twist.

Finally captured in 2011 after 16 years on the lam – and second only to Osama Bin Laden on the FBI's Most Wanted list – Bulger still maintains he wasn't an informant. Drug dealer? Of course. Killer? Hell, yes. But a rat? How dare we.