Peer pressure is tough, especially when it's pervasive, grown-up and institutionalized. In samurai movies, as in westerns, the warrior is often faced with a choice between individual morality and fealty to the tribe. Individual morality tends to prevail until society can be established and impose order, though in contemporary samurai movies, such as Jim Jarmusch's excellent "Ghost Dog," both choices can be rendered absurd by the circumstances. This is not entirely so in David Mamet's tricky and engrossing "Redbelt," a contemporary noir with a samurai movie interior, which is as sincere, plaintive and strangely optimistic a movie as he's made.

This society could care less about order -- it has embraced corruption at every level, and Mike Terry happens to be the only stoic-slash-chump, depending on how you regard him ("You're addicted to poverty," his disgusted brother-in-law tells him), who is bothered by this.

Ejiofor brings a calm magnetism and a beatific serenity to his roles that have the effect of knocking you flat -- there's something about this guy that's messianic. From his first moments on the screen, as he talks his star pupil, police officer Joe Collins (Max Martini), through a fight, ("Commit to the move," he tells him. "You know the escape. You know the escape."), he emanates a certain trustworthiness and levelheadedness that makes him seem like a bedrock of conviction. This is not a guy to be lead easily astray.

Of course, "Redbelt" being a Mamet movie (he wrote and directed), the noir puzzle element is central to the story, replete with double-crosses and other betrayals. Mike is one of two innocents (the other is Officer Joe) caught in a web that extends far beyond the parameters of professional fighting. It's a corrupt world in which morality and honor have been edged so far out that they're dwelling in the lunatic fringe.

Mike has asked Joe to stay after class at the academy one night when a distraught stranger named Laura Black (Emily Mortimer) comes in out of the rain to tell Mike that she has accidentally dented his car and wants to pay for the damage. A misunderstanding leads to her lunging for Joe's gun and taking out a plate-glass window. Joe decides not to report the incident, so insurance doesn't cover the window. For Mike's wife, Sondra (Alice Braga), this is the last straw.

Sondra, whose fledgling fashion business is helping float the academy, pushes Mike to ask her brother Bruno (Rodrigo Santoro) for a loan. Bruno is a nightclub owner and a fight promoter who has been trying to get his brother-in-law into the ring. But Mike refuses to compete, as "competition weakens the fighter." While at his brother-in-law's club, Mike happens to rescue a movie star Chet Frank (a restrained Tim Allen) from a bar fight, and gets a dinner invitation.

You know it's bad news -- this, it bears repeating, being a Mamet movie -- when the fine, upstanding guy is lured into the movie business, and Mike's radiant smile on the morning after his first set visit with Chet tells you all you need to know about what's next for him.

"I don't teach people to fight," Mike says on more than one occasion, "I teach them to prevail." You know in your heart -- or at least you hope -- that Mike will have it in him to follow his own lessons, but the movie makes a good case for how hard this can be when the fight is between what's morally correct and what's economically expedient. Mamet leads his fighter further into a trap from which it seems he won't escape. But he knows the escape. He knows the escape.