Redbelt, David Mamet's characteristically sinister take on the mixed-martial arts craze, is like a noir, grownup version of The Karate Kid or of the recent featherweight teen MMA drama Never Back Down.

Adult, in that it's no longer about being physically threatened by bullies in school hallways. In Mamet's world, the bad guys don't beat you up. They hem you in and cut you off, like a lab mouse in a maze where the only way out is the one they want you to take.

It's both the strength and weakness of Redbelt -- a movie in which everything is one big conspiracy that pushes our hero where he doesn't want to go. It's dark and creepy, but at the same time it requires us to (a) accept apparently wild coincidences as being part of a plan, and (b) ascribe a Machiavellian intelligence to lowlifes who otherwise appear to be as dumb as mud.

Redbelt sets up one pure-hearted character, a near-saint in fact, in mixed-martial arts instructor and ex-military man named Mike Terry (Chiwetel Ejiofor), whose instructional motto is "there's always an escape" and whose academy operates on a hand-to-mouth basis.

His prize pupil Joe Ryan (Max Martini) is an LAPD officer who idolizes his teacher to the point of being willing to take a bullet for him.

Terry's saintly foible is that he considers competition a stain on his art, even though he's married into a criminally inclined clan of Brazilian Jujitsu fighters and promoters who are intent on turning him into an attraction for their fledgling pay-per-view dynasty (Mamet's noir touch even makes the flash and gleam of TV coverage look dirty).

Then a series of apparently unrelated but remarkable things happen.

First, a distraught young female lawyer, looking for a late-night pharmacy to buy tranquilizers, hits Terry's car and comes in to confess. In her hysteria, she accidentally discharges Joe's gun, which shatters the academy window.

Second, Terry intervenes to save a drunken Hollywood actor named Chet Frank (a chunky and strangely low-key Tim Allen) who's getting beaten up in a bar. Soon Terry and his wife Sondra (Alice Braga) are having dinner with Chet and a producer played by Joe Mantegna and their wives, and being "set up" in the film world, both literally and figuratively.

Mamet, who is apparently a bona fide ultimate-fight fan, is big on metaphorical closeups of holds and escapes -- "escape" being Redbelt's central theme. And you have to give him credit for the imagination of his labyrinthean conspiracy plot.

It soon becomes a question not of who's "in on it" but who's not.

Still, all the machinations, dark lighting and F-words aside, Redbelt ends up in the same place as the popcorn movies it aspires not to be -- with a literal fight for redemption (though you don't walk away pumped up).

Ejiofor (Dirty Pretty Things) shines in this movie -- although nearly every other character is so flawed or slimy that it would be hard for him not to. It is inherent in the gloomy picture Mamet paints that to be a man of honour in this world is to be horribly alone.