Johnny Depp has been toiling under ten tons of hair and makeup for what seems like a decade now, often mistaking superficial transformation for quirky performance in movies like Mordecai, Alice in Wonderland, and The Lone Ranger. In “Black Mass,” a violent and visually sedate crime epic about the exploits of Boston’s notorious Whitey Bulger, Depp is once again caked in distracting prosthetics to resemble the kingpin’s weathered creepiness. Only this time, in spite of that over-the-top makeup, the actor manages to break the mold of diminishing returns and turn in a quietly captivating performance. On the page Bulger isn’t terribly complex, and it shows on occasion, but through Depp’s ugly (in a good way) accent and sneering, rotting smile we’re privy to a devil incarnate, a man simultaneously endearing and repugnant. He’s surrounded by a smorgasbord of great character actors, all of whom don the hard R’s and take to the dark tale with equal parts subtlety and theatricality. Joel Edgerton plays protagonist here as FBI agent John Connelly, a childhood friend of Bulger’s who means it when he calls himself a “street kid.” He’s never forgotten the protection Bulger provided him growing up on the mean streets of Beantown, and he’s willing to go pretty far in the name of neighborhood blood. Dakota Johnson surprises in a small role as Bulger’s one-time wife and mother of his son, a domestic subplot that manages shades to the monster even if the story of a familial gangster is quite familiar, to HBO viewers anyway. Benedict Cumberbatch isn’t so much miscast as he is unnecessary, donning his own upper crust New England sound to portray Bulger’s senator brother William, a somewhat thankless role that requires nothing more than unscrupulous charm, standard-issue for a politician. Besides Depp, the true standouts are Jesse Plemons and Rory Cochrane as the man’s right-hand men, bruisers who’ve stuck by Bulger through the years despite the grueling violence. Both are superb at displaying, ever so sightly, their increasing disillusionment with the boss’s brutal whims, a new found discomfort etched on their faces as they witness all manner of horror. Kevin Bacon, Adam Scott, Corey Stoll, Peter Sarsgaard, and Juno Temple round out the cast as an assortment of uptight cops and downtrodden criminals, most succeeding at conveying that distinct Bostonian flavor. “Black Mass” is chock-full of interesting gangsters, Depp’s Bulger chief among them, but Mark Mallouck’s script breaks little ground thematically as it doubles down on genre staples like loyalty, omerta, and the banality of evil. Adopting an unrelentingly oppressive tone, especially during the third act, that banality sometimes threatens the audience with that terrible possibility of boredom. Cooper reigns it in, however, with his taste for silence, such as one scene when Bulger and crooks pack in the back of a wagon and ominously cruise to a job somewhere, passing out guns like popcorn, or another where Bulger bullies his FBI buddies at the dinner table. A rarity in the age of rapid-fire editing, Cooper employs a welcome dose of stately tracking shots and slow dollies to incredibly suspenseful effect, proving himself a potentially remarkable if unreliable talent after “Crazy Heart” and “Out of the Furnace.” Narrative detours involving Bulger’s son and the IRA overseas are fresh enough to prevent that been-there-done-that feeling from truly affecting, and such a feeling can mostly be blamed on Marty Scorsese beating these guys to the punch with “The Departed,” an Oscar-winning Irish mafia pic not only set in Boston but partially inspired by Bulger’s life as well. By the end, while it’s hard to gauge the point of telling this relatively modest story, “Black Mass” is a menacing trip into those dark corners of Boston’s history.