For twenty years John Sayles has written, directed, sometimes shot, and always edited his own films. And for twenty years he has been a problematic filmmaker for me. He writes fierce stories -- "Matewan," "Eight Men Out," "Lone Star," among others, and most of them weightier than the entire life's work of directors like James Cameron -- but as a director, with the one glorious exception of "The Secret of Roan Inish," he is dull, obvious, and without imagination. He does not know how to use his camera to make his points, relying instead on set-pieces of dialogue performed in front of the camera. Two people talk, and Sayles cuts back and forth relentlessly in closeups from one to the other. He doesn't know how to move them in and out of frame, he can't let them focus on anything but what they're saying or hearing, they don't move, stretch, think, scratch, worry, grasp at meanings, or even get shocked. He's framed so tight on each of them that they might as well be acting in separate sets. It's one of the great disappointments of my life as a film critic that he hasn't given one of his scripts to another director, someone with a better feel for the kinetic power of film; we might, for once, have the joy of watching a masterpiece.

(And while I'm at it, I might as well point out that his editing is still first-year film school. He wants so badly to make sure we get his points that he holds every shot just a couple of frames too long. We sit in the audience waiting for him to catch up.)

And why is this so important in a discussion of "Limbo"? Because he has written nine-tenths of a brilliant film, cast it well, weakened it by dull and conventional directing, and then destroyed it by refusing to give it an ending.

The film is set in a port town in southeast Alaska, somewhere near Juneau, we assume. Donna DeAngelo (Mary Elizabeth Mastrantonio) is a lounge singer showing the effects of twenty years of small towns, small bars, and small men in her life, and at the same time confronting her heartbreakingly angry fourteen-year-old daughter Noelle (Vanessa Martinez), a school outcast but a brilliant writer and storyteller, who is not above self-mutilation as an alternative to screaming for help when no one can listen.

Donna has a long-term gig in that town, where Noelle has a summer job waitressing for a caterer. Noelle has a crush on fortyish Joe Gastineau (David Strathairn), handyman, former fisherman, once the local high-school basketball hero, now a sad, silent sack who gets by by not ever confronting his life. Naturally, he and Donna meet, test the waters, try things out, and begin to open up to each other in what just might be the start of something right. Sayles has written beautiful scenes of these two wounded birds trying to flex their wings for each other. And Mastrantonio, who sings live in the film, gives us a magical moment with the song "The Dimming of the Day" as Joe mans a fishing line out on the water.

But not content to leave well enough alone, Sayles insists that we spend some time learning what he wants to teach us about bad men who want to a) clearcut all of Alaska, or b) turn it into Disneyland North. Sayles is so intent that we not miss his point, that he has them talk only in the worst clichés of business-speak. Compared to them, the evil (and real) clearcutter Charles Hurwitz is a piker.

All of this is part one of the film. Part two begins when Joe's half brother Bobby shows up after some years away, to ask a little favor. Would Joe crew for him on a little trip down the coast, where he has to meet two businessmen? Joe doesn't ask, and Bobby doesn't tell, but we can guess that there's more to the trip than meets the eye, and we won't be wrong.

Joe takes Donna and Noelle along, thinking it's just a quick cruise through the Inside Passage, until the bad guys catch up with Bobby and our threesome must swim for shore to save themselves. Once on shore, with nothing but wet clothes, a knife, and a cigarette lighter, they are confronted with the task of surviving on an island out of the normal shipping or fishing lanes, with little hope of being found.

And it is here that Sayles finally gives us a sequence that is as moving, and gorgeous, and agonizingly powerful, as anything he's ever written. It is one of the great, breathtaking sequences in all of film. The little group of three, now a family, finds shelter of a kind in a long-abandoned homestead on the island. And Noelle finds a girl's diary buried in the dirt floor. As they sit around the fire, she begins to read aloud from it. The girl who wrote it and her parents came to the island to raise foxes and sell the pelts, starting over after lives of failure. Each night, Noelle reads another entry from the diary to Joe and Donna. And night after night we wait along with Joe and Donna to learn about this family as she reads each entry. We wait as early people waited each night for another chapter of the Iliad, or a Northwest Coast legend, or any of the great oral works that every culture grew up on. The story is gripping, and we ourselves are swept up in it. What will happen tonight? Will the foxes save them? We are like children, asking to stay up late and hear just one more chapter. And in Noelle's reading of the diary, what started out with high hopes slowly turns to sadness, illness, failure, and --

And what? This is the miracle of Sayles's writing. Because the diary, after the opening entry itself, is Noelle's own creation. It is the payoff of the film. It is whatever justification Sayles can claim for his work. It makes us cry with understanding and grief. It is the greatest moment of Sayles's whole career in film.

And then he destroys it. How? Because throughout this part of the film he has posed two plot questions: First, will someone find and rescue them? And second, will the people who find them turn out to be Bobby's killers, coming back to kill these surviving witnesses? They're fair questions, and we expect that they will be answered in one way or another. There has to be closure to something that the artist has so deliberately opened. So after holding out as long as possible, he teases us by showing us a plane coming toward them. What will it be? Rescue or death? Or maybe something else entirely? But at that moment, the very moment when he shows us that closure is at hand, he simply ends his film. It is not only unfair to his own construction, it is a copout both stupid and pointless. Is there a grownup around?