"Gaby -- A True Story" is the sort of movie that asks to be taken seriously, if for no other reason than its subject. And its subject is a tough one.

The movie, which was directed by Luis Mandoki, tells the life story of Gabriela Brimmer, a victim of cerebral palsy. Born in Mexico just after the Second World War, Gaby, as she's called, is for the first several years of her life thought to be either a vegetable or, to quote her doctor, a child of normal intelligence "locked inside a body that cannot respond."

The latter, in fact, turns out to be true. But it's not discovered until the maid Florencia (Norma Aleandro) notices Gaby fighting off her nanny's attempts to feed her by knocking away the spoon with her left foot. With her other limbs rendered useless by her illness, this foot becomes Gaby's only contact with the world, and with it she is able to communicate, by pointing to letters on an alphabet board or, later, by typing out her responses with her big toe.

Gaby (Rachel Levin) displays a genuine avidity for life. A bright and eager student, she passes an exam that allows her to progress beyond the limited special education classes available to her and attend the regular public school. Eventually she graduates from the University of Mexico, becomes a writer and publishes a book about her life.

Naturally, there are moments of despair, such as her disappointment over the collapse of her love affair with Fernando (Lawrence Monoson), another palsy victim, who is unable to break away from his domineering mother (Beatriz Sheridan) to make a life with Gaby.

But in telling Gaby's story, Mandoki has focused on the uplifting aspects of his heroine's life -- her triumph over despair. Still, Levin presents Gaby with a minimum of sentimentality. For the most part, she's a good-natured, resilient young woman who's equal to everything that life throws her way.

All of this is accomplished with the help of Florencia, who feeds Gaby, dresses her and becomes so close to her that she's almost an extension of her body. Gaby's story is to a great extent the story of this very special but peculiar collaboration. And it's the movie's greatest failure that the role of Florencia, who has given up her own life to nurture Gaby's, remains so unevolved. Aleandro's Florencia never becomes anything more than a blushing presence at Gaby's side.

Gaby's parents, Austrian Jews who immigrated to Mexico City after the war, don't make much of an impression either. Sari, played by Liv Ullmann, appears to abdicate her responsibilities as Gaby's mother with remarkable ease and very little guilt. Sari isn't uncaring; she's more a figure of weakness. And the crease down the middle of Ullmann's brow tells us less than we might hope to know about what's going on inside her.

As Gaby's father, Robert Loggia has a marvelous moment in which he looks deep into his troubled teen-age daughter's eyes, rolls off her sock and says, "What's up?" And when he's on screen, the movie has a directness and solidity that are missing at most other times. But Loggia's character, like most of the people in the film, remains distant.

The film's most interesting revelations have to do with Gaby's struggles for autonomy, her fight for an identity, even for a language of her own. But was there so little anger in Gaby? Mandoki emphasizes Gaby's determination and inner strength, but would it have been so bad if occasionally her motives were less pure? If, at times, out of anger or frustration, Gaby were cruel or petty or simply unthinkingly self-centered? Don't untainted role models create an extra burden for people with special challenges by asking them not only to overcome their disabilities, but to be paragons as well?

Gaby - A True Story, at the K-B Paris, is rated R and contains some nudity and adult situations.