"Weeds,"the new film starring Nick Nolte, takes a little getting used to. The movie tells the story of Lee Umstetter (Nolte), a convict serving a sentence of "life without possibility" at San Quentin, and practically before we've settled into our seats he's tossed himself over the third-story railing of his cell block and landed on the concrete below with an alarming smack. After recovering, he is slammed back into his cell and within minutes is dangling from the ceiling with his shirt knotted around his neck. Clearly, Lee wants to put an end to it, and, from this introduction you think that's what the movie is going to be about -- a man fighting to liberate himself from the hell of prison -- and in a way you're right. But what you don't anticipate is the manner in which the director, John Hancock, and his wife Dorothy Tristan, who together wrote the script, have approached their material.

There's very little about "Weeds" that you can anticipate, and that's part of its charm. It's got a fluky kind of originality and unexpectedness, the kind that isn't always by design. Having given up the idea of snuffing himself, Lee heads for the prison library and asks for a book -- the fattest they've got -- and the librarian plunks a copy of "War and Peace" down in front of him. No joke in that, really, but when on subsequent trips he picks up books by Dostoevsky, Nietzsche and, finally, Jackie Susann, the sequence becomes a nifty riff on the pratfalls of self-education.

Lee is energized by the world he discovers in literature, and after seeing a visiting theater troupe's production of "Waiting for Godot," he's transported. Revitalized, he begins writing his own play and with a company of fellow inmates, stages it for the other prisoners.

Naturally, it goes over big, not least because its subject is prison life and the innermost faults of the prisoners. But when the drama critic from a San Francisco paper (Rita Taggart) sees the play, she's impressed by it -- and perhaps more important, by Lee himself -- and begins the campaign for his release. Once out of prison, Lee moves in with his champion and begins to put his company, whose members are now all on the outside, back together again.

Based loosely on the experiences of former convict Rick Cluchey, who founded the San Quentin drama group and toured a production of his play "The Cage," the movie combines the usual craziness of a theater company on the road with the traumas of ex-cons trying to adjust to life on the streets.

It's a potent and original combination. It's not like any backstage comedy you've ever seen. At times, the movie gets hung up somewhere between slapstick and realism. But at others, like the scene in which a New York actor (Joe Mantegna) joins the troupe as a replacement and the ex-cons dream up a criminal re'sume' for him to use during the after-show question-answer sessions, the absurdism seems entirely organic.

Hancock and Tristan's script isn't shapely; the story moves forward as if it were being bumped along from the rear. It's the performers who really hold the film together. They share a smooth, spirited rapport; you get the feeling that they have done time together and know each other's moves inside out, but each stands out on his own as well. As the company's stage manager, Lane Smith is a marvelous nag -- he looks as if he should be wearing an apron. And as the light-fingered Bert, who liked prison because "it structured my life," William Forsythe looks like a baby who's been dropped on his head once too often.

Nolte, though, is the force at the center. Nolte has real weight as an actor, and he can be forceful without really exerting himself, without projecting. With his blocky, broad-framed body, he is a big man, but as Lee he plays the little man inside, the one who's afraid of blowing it and getting found out. Lee is a crook: Even parts of his play are lifted from Genet's "Death Watch." But Nolte gives him an almost childlike quality. And Lee grows in stature as the movie progresses; by the end he fills out Nolte's sturdy frame.

Weeds, at area theaters, is rated R and contains some profanity and sexual situations.