At one point in "Erin Brockovich" Julia Roberts tells her lover George (Aaron Eckhart), the Harley-Davidson biker and sometime construction worker, that she once was Miss Topeka, some inexact time ago, before her two marriages and three children, and before her subway-level job as a filer at the Los Angeles law firm of Ed Masry (Albert Finney). She was a trailer-trash woman who knew only that she had great looks. She only learned that she had brains to match when she spotted some medical files attached to real-estate records of home sales in the desert town of Hinkley, and went to see what they might mean.

What they meant (the film is based on a true story) was that Pacific Gas & Electric, the giant utility, was poisoning the ground water of the town by allowing chromium 6, a deadly carcinogen, to pollute it. Instead of acknowledging the action, the company hid it for twenty years and tried to cover it up by buying the town homes, saying that it needed the land for its power plant. Meanwhile, residents were sickening and dying without help or hope even to understand what caused their pain.

Now Brockovich, who dresses like a hooker but thinks like Ralph Nader, must tug, pull, harangue, insult, and badger the lazy, retirement-bound Masry into putting back on that cloak of public good and moral actions, and represent the citizens of Hinkley in a lawsuit against PG&E, and the rest of the film is the story of the lawsuit. It's also the story of what a woman with children must put up with if she is to make any kind of life for herself outside her home, and the film deals with that as well. She fights for her clients, and she fights for a decent salary for herself at the office. She fights with the loving George too, and learns from him that she's not the only one with needs.

Julia Roberts is so good looking, so sexy, so melt-in-the-mouth beautiful, with her enormous eyes and mile-wide smile, that it's easy to forget she has the acting chops to go with them; here she's presented with a real script and she has a ball with it. She is a thoughtful and witty and very human mother, she is an understated lover who shows the scars of previous relationships, and she is the fireball untrained legal assistant who marches through the workplace like a knife through butter. Then she has the wit to slow down to the pace of life and death in Hinkley, as she meets and signs up residents for the lawsuit. This is not a star turn but an actress working in character; she's so good we can't imagine anybody else -- we don't want anybody else -- playing the part.

The director is Steven Soderbergh, whose career since he blew everyone away with his first film, "Sex, Lies, and Videotape," has had its ups and downs. The ups include the noble failure "Kafka" and the powerful "King of the Hill," and the downs include the greatly overpraised, turgid "Out of Sight." Here he's found a good rhythm and let the script determine the pace. There are no directorial twitches, no monochromatic slo-mo sequences, just a lovely and loving recording of the events of the day, both personal and professional. The story, of course, is reminiscent of "Silkwood," "A Civil Action," and "The Insider," all in the tradition of liberal exposés of corporate malfeasance -- and let's ask why only liberals care about human life -- but shouldn't we be asking whether, in spite of everybody's hard work, in spite of all the exposés, and in spite of all the deaths by corporate action, whether we will ever make any kind of difference at all? I'm not hopeful.