If Lon Chaney was the “Man of 1,000 Faces,” then, by now, Johnny Depp is the man of 999. No current actor spends as much time in the makeup chair, film after film, as does Depp, whose actual face appears onscreen so seldom as to be almost unrecognizable. Yet, the vast majority of Depp’s grotesque characters—Jack Sparrow, Tonto, Barnabas Collins, the Mad Hatter, and the like—are more or less tongue-in-cheek cartoons rather than actual people, and even Depp’s villains are about as menacing as Yosemite Sam and Elmer Fudd. However, if 998 of Depp’s faces are played for laughs, his 999th, as gangster Whitey Bulger in Black Mass, is no laughing matter.

Although Bulger was infamous in and around the Boston area, his name was unknown by the larger portion of America that associates organized crime with the Mafia and predominately Italian gangsters. But when Jack Nicholson played a character patterned after Bulger in The Departed, curiosity about him grew. And when he was captured in 2011 after some 15 years as the FBI’s second-most-wanted fugitive (after Osama bin Laden) public interest skyrocketed. Now, with Bulger safely locked away for the rest of his life, the public finally gets to see what the fuss was all about.

As with many gangsters, Bulger’s life story is so bizarre that a fictional script depicting his various crimes and activities over the years would be rejected as being too unrealistic. Like many successful mobsters, Bulger came to power gradually over a number of years, often literally over the bodies of his rivals. But two things separated Bulger from most mobsters. First, unlike many mob bosses, he committed many of his murders personally, in some cases strangling his victims. And second, while the killings and other crimes were taking place, Bulger was protected by the law—not merely by corrupt local cops, but by the FBI itself, for whom Bulger served as an informant.

Black Mass focuses on the nearly 20-year period during which Bulger served as an FBI informant. According to the movie, FBI agent John Connolly (Joel Edgerton), a childhood friend of Bulger, recruits Whitey to help him get rid of the Italian mafia (in reality, it was probably Bulger who approached Connolly). Connolly confidently tells his superior (Kevin Bacon) that he can control Bulger, but it’s clear from the start that Bulger is merely playing Connolly. Bulger reveals as little genuine information about the mob as possible and continues his own criminal activities, including murder (the one thing Connolly told him he couldn’t do).

With the FBI’s tacit blessing, Bulger is able to expand his criminal empire, killing rivals and potential witnesses along the way, often in shockingly brutal fashion. He also manages to gradually ensnare Connolly in his activities by having the FBI agent cover and help conceal his role in the various killings. Connolly’s wife (Julianne Nicholson in an excellent performance) realizes what’s going on and tries unsuccessfully to stop him. Eventually she receives a none-too-subtle threat from Bulger personally.

The only person who does not get directly involved in Bulger’s activities is his brother John (Benedict Cumberbatch), a Massachusetts state senator who won’t help Whitey but also won’t help the authorities track him down. One of Black Mass’s biggest shortcomings is the fact that it doesn’t explore the relationship between the brothers in greater detail.

For those unfamiliar with Bulger’s criminal history, Black Mass will probably be a confusing movie at times. Director Scott Cooper frames the movie through statements given to the police by various Bulger associates after their arrests, so the film is told in a somewhat haphazard, episodic fashion. Numerous characters come into the movie with little explanation, and many important events are glossed over through various montages.

Ironically, the FBI’s inept investigation into Bulger’s activities is easier to follow than his actual crimes. Bulger keeps the FBI at bay by promising to inform on the Mafia, which is regarded as the more dangerous criminal organization. Bulger’s operation, known as the Winter Hill Mob, is viewed by the FBI as a strictly small time crew, a misconception that Bulger is happy to indulge. Only after a new prosecutor (Corey Stoll) begins looking into Bulger did his house of cards collapse, taking Connolly and numerous others down.

On the other hand, as a character study of a particularly repellant psychopath, Black Mass is excellent.  Whitey Bulger may well be Johnny Depp’s best role yet and he’s got an excellent supporting ensemble. While the big picture may be confusing at times, director Scott Cooper adds a number of small scenes to the movie that round out Bulger’s personality. He might be a monster, but he loves his mother and is deeply hurt when he has to watch her funeral from a hiding place in the church to avoid unwanted publicity. Similarly, he grieves after the death of his six-year-old son and at his helplessness in preventing the disease that claimed the child.

Of course, Bulger shows no sympathy or remorse for those who anger him, often murdering them in exceptionally savage fashion (he strangles the girlfriend of one of his gang members to keep her from talking). But it’s the quiet scenes that show Bulger at his most dangerous. In the film’s most chilling scene (one that will rival Joe Pesci’s “am I funny” scene in Goodfellas for creepy menace), dinner table banter with one of Connolly’s fellow FBI agents turns potentially deadly when the man tells Bulger his “secret family recipe” for marinade. Bulger then asks if the agent would inform on him as easily as he would reveal the marinade recipe. That scene alone, without overblown histrionics or fits of anger, should be enough to earn Depp an Oscar nomination.