"Tarnation" isn't quite a documentary but what might be called a self-documentary, or possibly -- here's an outstandingly ugly neologism -- an autobiogumentary. In it, a young man assembles the detritus of his existence -- photos, old home movies, video -- to chronicle the life of his desperately ill mother. Of course, he also chronicles the life of himself. Endlessly. In fact, there are so many close-ups of Jonathan Caouette, you sometimes think the movie should have been called "And Here's Johnny!"

His narcissism aside, the artifact he cobbles together is mesmerizing. It tells -- when her son hasn't placed himself six inches from the lens of his Super 8 -- the story of poor Renee LeBlanc in the most intimate tone possible. If the movie got any closer, it would be wearing her lingerie.

Narrated with child's-book simplicity in title cards, it discovers a beautiful young Texas girl who fell victim to barbaric mental health practices in the '50s and never quite recovered. Renee was so gorgeous as a child that she had a career as a regional model and TV commercial star. But after a fall off a roof and six months of hysterical paralysis, she was diagnosed as "mentally ill" and given dozens of shock treatments. That Gzzzzzppp you hear is brain cells melting. If she wasn't damaged before, the treatments certainly guaranteed damage after.

Becoming dreamy and disengaged, she fell in love with, married and was deserted by a young man named Steve Caouette. She then discovered she was pregnant with Jonathan. She tried to raise him alone -- the old home movies show a grave, beautiful child, with blond hair and gigantic, sad eyes -- but it was too much and psychotic episodes continued, including an irrational and penniless trip to Chicago where she was raped before his eyes. Ultimately she was committed and he was sent to foster homes (and abused), then returned to his grandparents, Adolph and Rosemary Davis, who tried to raise him as best they could.

For whatever reason, he was not your usual Texas high school kid. He was drawn to theater, to movies, to wild self-dramatization and seems to have developed a lifelong habit of filming himself performing solo for the camera. On the evidence here, he loved to vamp in a kind of prepubescent drag, or to portray himself grotesquely wounded or in other forms of extreme derangement.

Meanwhile, the poor Davises struggled as best they could with the burden of the lost daughter and the over-the-top grandson, who himself (he admits candidly) developed mental difficulties frequently expressed by destructive rages within the home, suicide attempts and drug experiences.

Jonathan evokes all this chillingly, with snippets of home movie, tape recording, photo montages; as a visual document the film is quite compelling and it's remarkable how vividly he can evoke his childhood from such sketchy data.

Once he moves, at age 20, to New York, it all seems to get better: He finds himself as an actor, as a gay man, as a videographer. We meet his lover and the little community of pals he settles into. Eventually he becomes kind of friendly with his mother, who is probably at her best when she comes to visit him. There's even a roughly funny scene -- self-photographed -- in which the father and husband, vanished these many years, returns and the three of them try to get along.

But soon enough Renee just wears out; she returns to Texas when her mother dies, and comes to live with her aging father in a once-tidy middle-class home that has become a cesspool; her father is now addled and paranoid (he forbids Jonathan to film him anymore) and she's disconnected from reality.

What the film offers, if you can get past the vanity inherent in much of it, is a glimpse of a reality that almost never makes it into drama. There's a sense of how some people turn out badly, and how some dreams don't come true, that's exceedingly powerful. You may not want to hang with the haunted Caouettes, but the movie is so compelling, it doesn't give you a choice.

Tarnation (105 minutes, at Landmark E Street) is not rated but it has some nudity and fleeting scenes of gore.

Renee LeBlanc, a gripping character in her son's film.