With Martin Scorsese, American cinephiles had their first geek hero: a scrappy, street-smart provocateur with a gift for stylistic flourish. Bursting onto the New Hollywood scene in the mid 1970s with a string of gritty, critically acclaimed movies about New York street life, he quickly gained a reputation as an edgy chronicler of the hair-trigger world of tough-talking criminals.

But even thick-skinned street-geek outsiders like Scorsese occasionally succumb to the pull of the establishment. In the mid ’90s, backed by the promotional muscle of the Weinstein Brothers, the director struck out for Oscar gold with Gangs of New York and The Aviator, two lavish but stilted period productions that, despite their scope and production values, failed in their trophy bids. Now, with The Departed, the director has returned with a guns-blazing reclamation of his old crime-movie turf. Once again delving into the brutal machinations of the criminal underworld — albeit in Boston rather than New York — he has fired off his most ferocious, explosively entertaining film in more than a decade. Crime may not pay, but for Scorsese (and his fans), crime movies most certainly do.

The Departed is a remake of the slick Hong Kong cop thriller, Infernal Affairs. Like that film, it tracks the intersecting stories of two moles — Billy Costigan (Leonardo DiCaprio), a cop gone undercover as a criminal, and Colin Sullivan (Matt Damon), a criminal infiltrating the special state police unit assigned to bust a big-league Boston crime ring run by thug king, Frank Costello (Jack Nicholson). As if their lives didn’t parallel enough, both Billy and Colin become involved with a police shrink named Madolyn (Vera Farmiga), who serves as a sort of connective tissue between the two men. Meanwhile, mid-level cops played by Martin Sheen, Mark Wahlberg, and Alec Baldwin bicker over departmental turf, and a slew of surly Irish thugs act as enforcers in Costello’s army. In typical Scorsese fashion, it’s a sprawling, hot-blooded mess of clashing egos and personal vendettas.

Scorsese and screenwriter William Monahan have expanded the film’s back-story and added depth to some of the characters — especially Nicholson’s vicious crime boss — but for the most part, they are remarkably faithful to their source material, replicating all of the major plot points, much of the dialog, and even some of the staging and set design. The additional length gives the film a looser, more padded feel than the taut, plot-driven original, but what little is lost in tension gets made up for in depth.

Scorsese made his name as a low-budget master stylist — a sort of American Godard whose deft incorporation of pop music, visionary camera moves, and hyperactive montages were designed to call attention to the artifice of filmmaking. Here, his directorial signatures are fully evident, with manic editing, paranoid zooms, and breathless pans all stirred into a raging cyclone that howls to a soundtrack of 60s protest rock and modern-day Irish pub punk. It’s a hopped-up visual match for the feisty, ready-to-rumble ethos of his street tough characters.

Scorsese may not have invented the pop-music soundtrack, but one could make a good argument that he perfected it. In The Departed, he looses a barrage of tone-setting tunes on nearly every scene; the movie is textured as much by the music as by its whirling camera. If Scorsese hadn’t become a crime-film auteur (or, as he originally intended, a Catholic priest), he might’ve been a D.J.

Befitting the dual narrative, the director crosscuts continually between the two main characters, harshly breaking out of their respective individual scenes to remind us what the other one is up to; it’s Scorsese’s way of reinforcing both the connectedness of the characters and the way they’ve each battered down the entrance to the other’s domain.

As the criminal-cop and the cop-criminal, Damon and DiCaprio each make the most of their juicy roles by deploying their personalities to deceitful ends. Damon manipulates both his colleagues and girlfriend with brutal precision, wielding his Ivy League charm like a jackknife in a back-alley brawl. DiCaprio, surprisingly effective as a hot-tempered lout trying to do the right thing, works his way up the criminal food chain through actual brawling. It’s a smart reversal — letting the criminal float by on good looks and charisma while the cop pummels through the landscape, volatile and reckless.

Like many films to come out the bullet-riddled Hong Kong crime genre (most notably John Woo’s Face/Off and The Killer), Infernal Affairs used its cop/criminal equivalence as an expression of yin and yang Eastern dualism. In The Departed, Scorsese and Monahan trade notions of philosophical balance for an exploration of the more traditional American conflict between public and private identity. As Costigan and Sullivan dive further into their assumed lives, their identities threaten to become compromised — not only to those around them, but to themselves as well. The film’s central question seems to be whether anyone has an identity apart from what he or she does. Can a cop be an effective criminal, or a criminal a convincing cop? And if so, at what cost? The film hints that truly knowing anyone — including one’s self — is impossible; one can only know what people do.

As the aging crime kingpin Frank Costello, Jack Nicholson certainly shows off his bloody doings. At 70, the actor is starting to show some wear and tear, but he turns his frailty into menace by playing up his decaying, erratic behavior. His villainy is an impenetrable mix of brutality and entitlement. “A lot of people had to die for me to have the life I’ve had,” he says, showing neither glee nor regret at what seems to him to be an indisputable fact of life. Evil like this, the film suggests, cannot be rationalized by history or circumstance.

Throughout his career, Scorsese has always shown an unflinching eye for man’s folly and a keen grasp of the mysteries of human intention. Part of what makes the filmmaker so electrifying is that he can seem as uncertain and hesitant about what’s going on onscreen as those of us in the audience. What lurks in human hearts? That’s the question Scorsese has long asked. In The Departed, his answer, as always, is that while no one knows for sure, it must be dark indeed.

– Peter Suderman is assistant editorial director at the Competitive Enterprise Institute. He blogs on film and culture at www.alarm-alarm.com.