I'll get to the details of David Cronenberg's Eastern Promises in a bit, but first a few words about star Viggo Mortensen, because after you see his work in the powerful thriller, you'll likely want to know more about him. Mortensen, who appeared as the heroic Aragorn in the Lord of the Rings movies, made his screen debut in 1985 as an Amish farmer in Witness and had significant roles in The Indian Runner, The Portrait of a Lady and G.I. Jane, but the first time I really took notice of him was in 1998's A Perfect Murder, where he co-starred with Michael Douglas and Gwyneth Paltrow as a creepy-sexy artist sleeping with the missus. The film was strained, to say the least, but Mortensen made a strong impression, playing an erudite thug.

The thing about Mortensen is that, no matter what the background or nationality of his characters, he always comes off as authentic. Not showy authentic, either. Without making a big to-do about it, he manages to be so convincing that you find it hard to believe his real background or nationality isn't similar to that of his character. After watching his dead-on performance as a Russian in Eastern Promises, I came straight home to find out once and for all where Viggo Mortensen was born and bred.

Turns out he was born in New York City to a Danish father and an American mother. The family later moved to South America, where Dad managed chicken farms in Venezuela and Argentina. At 11, the boy moved back to NYC with his mother when his parents split up. After graduating from college, he relocated to Denmark, where he spent several years before returning to the States. Clearly, Mortensen drank in the various cultures to which he was exposed, and his father's work ethos as a farmer appears to have had a major impact as well. The actor is fluent in English, Spanish, Danish and French, and reportedly also speaks pretty good Swedish and Norwegian.

Not Russian, however, though you'd never guess after watching him in Eastern Promises. There are a great many sterling performances in Cronenberg's gripping story of first-generation Russian mobsters in London, but Mortensen anchors the movie. He also gets brutally knocked around while stark naked in a devastating fight sequence set in a steam room.

After making people like me extremely uncomfortable with bizarre psycho-sexual films like Videodrome, Dead Ringers and the car wreck fetish flick Crash, David Cronenberg is working in a more conventional fashion lately. Re-teaming with Mortensen following 2005's A History of Violence, Cronenberg focuses on what happens when a young woman dies in childbirth and the midwife (Naomi Watts) reads her diary, leading her into the world of organized crime. Mortensen is a driver for the loose cannon son (Vincent Cassel) of the mob boss (Armin Mueller-Stahl).

The mood is low-key, but taut, punctuated with flashes of shocking violence. The story is consistently involving, with twists and turns throughout. There are a couple of moments where the verisimilitude is disturbed by overt exposition and an instance of too-traditional dramatic staging, but they pass quickly. Bottom line: Eastern Promises is a superbly acted, atmospheric thriller that pays off on a number of levels. Get ready to tense up.