We're in the home stretch of 2006, and the movies have already begun getting longer and more important. Critics will be on the lookout for movies chock full of social and political messages to justify their choices as the year's "best," but let's not forget the artistry of crafting a movie that very simply feels right and moves well. One of the greatest films of all time -- some say the greatest -- is F.W. Murnau's Sunrise (1927), a movie based on nothing more than the most wretchedly old-fashioned love triangle. (Sexy, evil city girl seduces farmer away from his simple, loving country wife.) But Murnau took this story and turned it into cinema poetry. Every shot in some way physically represents the inner turmoil of the characters.

Few filmmakers today can accomplish this; Brian De Palma did it in The Black Dahlia and Martin Scorsese does it in The Departed. A cursory glance at the two films reveals that The Departed is far more accomplished and skilled, but that's deceptive. The difference is that De Palma makes his story serve him, while Scorsese serves his story.

For the first two hours, The Departed moves with a fury, switching and leaping like an extended version of the drug-induced GoodFellas (1990) climax. Even if characters merely sit talking in a room, the camera zooms and tracks and swishes, and editor Thelma Schoonmaker cuts exactly on the beat. But toward the end of its 149 minutes this energy begins to flag. Scorsese and his screenwriter William Monahan (Kingdom of Heaven) begin to worry about how to wrap things up; they start cramming in conclusions every which way. The final couple of scenes play as if everyone just wanted to go home.

Still, even though The Departed doesn't quite reach Scorsese's peak, it could well be one of the year's best films. It lacks the gaudy grandeur of something like Casino (1995) or The Aviator (2004), but it's also not as compact as Mean Streets (1973) or Bringing Out the Dead (1999). In this, it might have taken a cue from Andrew Lau and Alan Mak's superb, taut 100-minute Hong Kong action film Infernal Affairs (2002) upon which it is based. (Though Scorsese does include a clip of John Ford's beautiful, Oscar-winning Irish gangster film The Informer, from 1935. A hint to the Academy?)

The story follows two cops/criminals: the first, Colin Sullivan (Matt Damon), works for a Boston gangster, Frank Costello (Jack Nicholson), and operates as a mole within the police department. The second, Billy Costigan (Leonardo DiCaprio), is an undercover cop who poses as a member of Costello's gang. Both rats have burrowed so deeply undercover that their true identities hang by a tenuous thread; they don't even know each other. Sullivan answers only to Costello, while Costigan secretly reports to the good cop-bad cop team of Queenan (Martin Sheen) and Dignam (Mark Wahlberg).

The Departed adds a further complication: a blond, blue-eyed police shrink (Vera Farmiga) who links up romantically with both protagonists. Last fall Farmiga earned year-end accolades for her performance as a junkie and mother of two in Down to the Bone, a very good movie that barely opened and hardly anyone saw. But that notice catapulted her straight to the fast track, and now she's working with Anthony Minghella in Breaking and Entering as well as with Scorsese.

Every actor in Hollywood wants to work with Scorsese, and he honors them all; Alec Baldwin tosses off a few snappy line readings, while spot-sweating through his blue cotton shirt. Ray Winstone makes a touching thug, and Anthony Anderson finds the pathos within his happy-go-lucky comic persona. These actors actually appear to be concentrating on one another, listening to each other and pausing to think of what to say next; the performances are deceptively, deliciously natural.

DiCaprio is slowly becoming a commanding lead, his baby face hardening into something granite-like, but with room for worry, fear and anxiety in his changeling eyes. He's better here than perhaps ever before.

Yet, one wishes that Damon had played his role a little less like a traditional villain and more like Costigan's equal. Damon starts out as a charming heavy -- reprising his Good Will Hunting Boston accent -- but with a new suave demeanor and harsh confidence. As the movie goes on, he allows his certainty to slip away, and he begins to sweat, making it all too obvious that he's guilty and hiding something. (Several scenes, such as one in which he's caught examining surveillance camera footage, are dead giveaways.)

Above all, Nicholson nearly steals the entire film with his hilariously offensive tidbits of wisdom, but this is Scorsese's domain, and his presence is behind every gorgeous shot.

One breathtaking moment simply has Sullivan and Costigan "meeting" for the first time over cell phones; they're framed exactly the same, shocked silent by fear and anticipation. Here technology connects everyone, as does violence, ranking everyone at the same level. Costello speaks a line early in the film (and in the trailer) about how one can be either a cop or a criminal, but when there's a loaded gun pointed at your face, what difference does it make?

Scorsese doesn't answer that question, nor does it matter. He has ceased fighting the personal demons that haunted Taxi Driver (1976) and Raging Bull (1980). Now he's here to demonstrate the sheer infectious pleasure of making cinema, a glorious symphony of motion in the key of violence.