The 2002 Hong Kong crime thriller ''Infernal Affairs" arrives in Boston riding two years of hype among fans of the genre -- all of whom have doubtless long since seen the movie and its two sequels on their hacked all-region DVD players.
For everyone else, it may help to know that ''Affairs" was a box office sensation in Asia, that Martin Scorsese will start production on the inevitable American remake here in Boston next March (retitled ''The Departed," it will star Matt Damon and Leonardo DiCaprio, with the part of the Triad criminal organization played by the Irish mob), and that the original film is itself quite possibly the best Michael Mann movie that Michael Mann never made: sleek, chic, and broodingly fatalistic.
The concept is so high you can barely make it out, at least in the opening 15 minutes. Essentially, the Hong Kong police and the Triads have had the same idea at the same time: place a young undercover mole -- a lifer -- on the other side and have him feed information back for years. So Yan (the great Tony Leung, of ''Hero" and ''In the Mood for Love") is ostensibly booted out of the police academy and works his way slowly up the rungs of criminal enterprise until he sits just below Sam (Eric Tseng), the laughing buddha of Pacific Rim drug distribution. And Ming (Andy Lau, no relation to codirector Andrew Lau but an HK film dynamo in his own right) has been sent by Sam to rise through the ranks of the police force until he is at the right hand of supervisor Wong (Anthony Wong).
And that's just the setup. The main action of ''Infernal Affairs" consists of the cops and the criminals moving forward in parallel lockstep, each mole trying to sabotage the other side while uncovering his opposite number at the same time. Ming is promoted to internal affairs to oversee the effort -- like Kevin Costner in ''No Way Out," his new job is to catch himself -- while Yan stalks his mirror image on the force and communicates with the supervisor by Morse code. To Ming, he's just a ghostly series of clicks.
Those who come to ''Infernal Affairs" expecting Shaw Brothers grindhouse mayhem, stylized John Woo violence, or airborne martial arts will go home disappointed: Directors Lau and Alan Mak keep things muted and tersely procedural, with spasms of gunplay serving only as punctuation. Andrew Lau also served as cinematographer, with an emphasis on blues, chrome, and glass -- crime thriller as echo chamber.
The pleasure of the film is in watching Lau and Leung play matching moles who, after a decade undercover, resemble each other more than any of their colleagues, and in keeping up with the script as it piles reflection upon reflection. Both men barely know who they themselves are anymore, or to whom their loyalty should go. Sensing his psychic distress, Ming's girlfriend, Mary (Sammi Cheng), is even writing a roman clef about a man who starts role playing the moment he wakes up. (Yan's love interest, meanwhile, is pure, goofy HK invention: a gorgeous court-ordered psychiatrist played by singing megastar Kelly Chen.)
Lau's cool yuppie mask as the undercover criminal plays effectively against Leung's earnest agony as the undercover cop, and ''Infernal Affairs" keeps curling satisfyingly about itself until Yan and Ming come face to face, whereupon a few final curveballs come flying through the screen. Unlike the two sequels, though, the original plays fair. It also ventures far enough into the politics of identity to pass for an art film. Almost by accident, Lau, Mak, Lau, and Leung seem to have backed into a Hong Kong action remake of Ingmar Bergman's ''Persona."
Ty Burr can be reached at email@example.com.