The thing about David Cronenberg is that while he may be artsy, he's never fartsy.

No matter what high-falutin' idea or theme he may be rolling out, you can always count on Cronenberg to blow up somebody's head or show some slimy thing crawling beneath someone's flesh.

In his Russian mafia underworld saga, Eastern Promises, Cronenburg plays around with a motif that's officially reached trend status - in a world riven by violence and nearly lost to madness, some men are still decent enough to be moved by the life of an innocent child, our dim hope for the future (see also Children of Men, and last week's Shoot 'Em Up).

How violent? In one early scene, mob foot-soldier Nikolai (Viggo Mortensen) enacts the best finger-severing scene since Darkman. He's a real stylist. Before he commences the cutting (all 10 digits!), he extinguishes his cigarette on his own tongue. Bravo.

Mortensen, who also worked with Cronenberg on A History of Violence, has now completed the task of oblitering any risk that he'll be typecast as the guy who ascended the throne of Gondor.

In Eastern Promises, he plays the gaunt, tattooed enforcer for a London crime boss (never mind whom, it's part of the plot) whose operations include the drugging, defiling and slaving of underage girls, brought in from the former Soviet Union (Nikolai makes his bones, so to speak, by raping one).

One of these unfortunate girls lives just long enough to give birth, in an emergency room, to a little girl. A midwife (Naomi Watts) tries to find the father, leading her into the dangerous mob underworld, endangering herself, her family and the child.

Cronenberg does something narratively unusual in Eastern Promises, something that almost doesn't work. He tells the story from the point of view of Watts, with Mortensen as a minor supporting character. The movie slowly pivots, then, until Mortensen is its star and Watts the distant supporting player.

It helps that the second movie, Mortensen's movie, is by far the better one. The drab, strangely predictable story of the search for the baby's father gives way to a more engrossing, at times exciting saga of a war among rival mobs, complicated by Nikolai's tricky allegiance to a kind of Russian version of The Godfather's Fredo (Vincent Cassel).

All gathers momentum to a spectular, gritty knife fight in a public bathhouse, during which eyeballs are stabbed, hamstrings cut, and Lord of the Rings fans get to see what Aragorn looks like without his robes.

No hobbit jokes, please.