It can be a film-buff parlor game to try to decipher David Cronenberg's ideas, but in movies as diverse as A History of Violence, Crash, Spider, Dead Ringers, and The Fly, it's aggressively apparent that they are films of ideas. That's what makes his new one, Eastern Promises, so intriguing. It's an academic meditation in underworld-thriller drag a movie that looks about as close to a straight-ahead, down-and-dirty genre entertainment as anything the director has made since his exploding-head horror days. Just give it a while, though. In London, a dazed 14-year-old, with purple track marks on her arm, collapses in a bloody heap. Anna (Naomi Watts), a hospital midwife she's English, but of Russian descent watches helplessly as the girl dies in childbirth, then attempts to locate the baby's relatives.
Her one clue is a diary, written in Russian. It leads her to an elegant restaurant, in the city's Russian demimonde, run by Semyon, a grandfatherly gent played by the great sly dog Armin Mueller-Stahl with such soft-spoken benevolence that from the moment he volunteers to translate the diary, you just know he's bad to the bone. A thriller can lead us into the fascinating intricacy of a criminal subculture, and Eastern Promises does that with the globalized Russian Mob. The whackings have their own brazen operatic flavor, and so does the ritual of becoming a ''made'' man (it involves special tattoos). A prostitute den is stocked with morose Slavic Valkyries a relevant setting, since the film explores sex trafficking.
Even more vivid, though, are Semyon's son, the sneery, hotheaded Kirill (Vincent Cassel), and his driver, poker-faced Nikolai (Viggo Mortensen), who is angling to move up in the family business. (Semyon treats him like a second son.) Both carry a beyond-cool mystique of solemnly heartless old-world machismo. Nikolai, toughened by his time in Soviet prisons, is a particular enigma: a dashing statue of a man, at once calculating hard case and noble knight. He woos Anna, who has no idea that he's a gangster, and begins to win her over with his frosty-eyed reticence.
Eastern Promises unpeels like an onion of corruption, with double crosses and deceptions, and ordinary do-gooders (like Anna's crusty old uncle) in way over their heads. Cronenberg's craftsmanship is seductive, yet anyone waiting for a conventional resolution, or even a coherent one, will be soundly disappointed. The film's key sequence is an amazingly vicious fight in which Nikolai, naked, fends off two dagger-wielding assassins in a steam bath, grabbing their weapons and plunging them again and again. And again. Cronenberg, riffing on the strategy of A History of Violence, wants us to gaze at Viggo Mortensen and see not just a man but a paradox, a walking deconstruction of humanity's dual nature: good and bad, immersed in a violence so brutal it can only have come from evil, even if it's being used for justice. But this is all a bit much to pile onto a conventional heart-of-darkness thriller. Eastern Promises is a decent night out, but in delivering ''more'' than it promises, it also delivers less. B