Martin Scorsese's "The Departed" is perhaps the most cheerful movie about a fierce and vicious culture of brutality ever made. It opens with shades of the director's great "Goodfellas," but as freely and devastatingly as the blood flows in the final third, this is never a movie about consequences. The film is a legacy thriller to the bone, setting up the most happily contrived cinematic duel since "Face/Off" and running with it, for the most part convincingly, through a bird's-eye tale of loyalties lost and almost romantic deceit.

It's a story that could only have been sold by a director like Scorsese, who makes the film's narrative inconsistencies seem like a commentary on the essential nature of man. Anyone who moves a camera this seductively has and should have the undying confidence of his audience, but with "The Departed," Scorsese's heavy hand as a filmmaker comes down a little lighter. After a decade of films received with ambivalence and faint praise, here is the kind of sprawling popcorn movie for adults that has been out of fashion for some time. It feels like a quintessentially American movie, if not thematically then aesthetically, which in a way is ironic, since the film is technically a remake of the 2002 Chinese thriller "Infernal Affairs."

The main plot stays largely intact, save for an increased prominence of the Jack Nicholson character (a no-brainer that surely had more to do with the actor than the part) - fascinating given that the story was originally a cultural fable of morality and loyalty that has now been adapted seamlessly for an American audience.

The new screenplay has the same stops but new details. In a tough Boston neighborhood "some years ago," a mobster takes a boy without a father under his wing. The boy becomes a man, Colin (Matt Damon), and on the day of his graduation from the police academy, his godfather (Nicholson) is there.

Later another young man, Billy (Leonardo DiCaprio), graduates from the same academy, but his transition into the police force is stalled. As with all the characters here, he has an obvious history hinted at but never explored, and is tapped by the department to go undercover with the city's most infamous mobster (Nicholson).

The dichotomy is clear enough. As Billy gets in with Costello (a little too effortlessly), Colin rises the ranks of the local PD, and the two moles - which the film goes to great length to remind us aren't very different from each other - end up in tug of war for power both tangible and otherwise. If it all sounds too busy, it is, but Scorsese, working from William Monahan's richly textured screenplay, plays down the convulsion and narrows in on the more obvious back-and-forth between the two leads.

As Billy, DiCaprio works hard to shake off the boyish innocence and renegade aloofness that made him a pin-up and consequently a star in the mid '90s, a sense of insecurity he should have outgrown some time ago. Scorsese is director with a careful eye for talent, and once he thinks he's found it, he sticks with it: The actor has now headlined his past three films, and as intensely as he throws himself into his roles, he's proven himself dedicated but not entirely in control of his medium. Damon, consequently, is a strange fit as his double, a star whose presence as an actor (if not his bankability) has never been in question. Nicholson nails his part, but only customarily so, coasting through because he knows he can. The list goes on, and should, since the film boasts one of the most uniformly terrific ensemble acting of the past decade. This is a group of people who all understand their roles precisely, and the intensity of their commitment is paramount to the movie's success.

The film's weakest moments are its final ones. The last half hour is as bloody and unsparing as the exposition would suggest, but the characters' logic is quickly lost in the crossfire. It's true that a movie like "The Departed," where the story's contrivances are brushed past defiantly, has no real responsibility to the audience to end with more reserve (really, an ending less drastic would probably have been an anticlimax), but the final scenes are the only time the screenplay's otherwise modest allegory seems to be running the show. The film gives into the temptation to make efficient sense of its narrative too easily, and in a movie all about execution, very little about concept, it's a misstep that couldn't be more pronounced.

4 out of 5 stars