Erin Brockovich, a twice-divorced, unemployed mother of two young children and an infant, consults lawyer Ed Masry of the Van Nuys, California firm Masry and Vititoe, regarding claims for injuries she suffered in an automobile accident that was not her fault. Although Ed assures her that he can get her a large settlement, he loses the case. Some time later, Erin, who has been unable to get work, bullies her way into a job as a file clerk with Ed’s firm. Erin also meets a new neighbor, George, who has a passion for motorcycles and whom her children adore. One day, while filing, Erin comes across a pro-bono case against the San Francisco-based Pacific Gas & Electric Co. that Ed is handling on behalf of residents of Hinkley, California. When Erin asks Ed if she can assist with the case, he absent-mindedly agrees and Erin soon drives to Hinkley. There she meets with housewife Donna Jensen, who explains that both she and her husband Peter are seriously ill and that PG&E, a significant presence in the community, has been paying the family’s medical bills as well as trying to buy their house. The Jensens suspect that hexavalent chromium, known as Chromium 6, in use at the PG&E plant, may be causing their illness. Later, Erin learns from a UCLA professor that chromium 6 is added to water as an anti-corrosive and that certain levels of chromium 6 contamination can cause all kinds of illnesses, some of which can prove fatal. On the professor’s recommendation, Erin goes to the Lahontan Regional Water Board, which serves Hinkley, and by playing up to the naïve young, male clerk, is able to browse through hundreds of old records. Her rearch uncovers a cleanup and abatement order to PG&E to remove hexavelent chromium, because it is contaminating groundwater over a large area. When Erin returns to Ed’s office, she learns that she has been fired, as he had misunderstood what she was doing. At home, although Erin is reluctant to become involved with another man, she begins a relationship with George. Later, Ed comes to see Erin, who is still unemployed, to tell her that the UCLA professor has examined the papers she found in Hinkley and concluded that the levels of chromium there could be responsible for the cancer in the Jensen family. Ed apologizes to Erin and, after she apprises him of her other discoveries, is persuaded to rehire her, with a raise and benefits. Weeks later, a PG&E representative meets with Ed and Erin and informs them that the company has made a generous offer to buy the Jensens' home, but denies any responsibility for their medical expenses. Soon, Tom and Mandy Robinson, who used to live across the street from the Jensens, come to tell Erin that Mandy has suffered five miscarriages and that their chickens have died with strange tumors, prompting them to wonder if they are also victims of the chromium use. Ed and Erin then go to Hinkley, meet with other residents and inform them that his firm will represent them against PG&E. If they win the case, his fee will be forty percent of whatever is awarded, but if they lose, his fee will be zero. Erin then interviews several other families with serious illnesses, hoping to add more families to the claim. Although Ed, who is close to retirement age, begins to worry about battling a giant company like PG&E, knowing that they could keep him in court, at great expense, for years, he is willing to continue, if Erin can produce significant evidence. Erin then collects water samples around Hinkley. Nine months later, Ed and Erin attend a community picnic in Hinkley, seeking to add more names to their growing list of four hundred and eleven plaintiffs. The case is costing a great deal and Ed is forced to take a second mortgage on his house. He feels that the punitive damages claim hinges on whether the PG&E head office in San Francisco was aware of what was going on in Hinkley and uses a legal ploy of bringing a preliminary suit against PG&E in the San Bernardino County Court for damages and medical expenses due to ground water contamination. Although PG&E submits a motion to strike the claim, the judge rules in favor of the residents and reprimands PG&E’s lawyers, who later offer Ed and Erin a twenty-million dollar settlement, which they decline. Meanwhile, Erin’s relationship with George and her children is deteriorating, as she is seldom home. George asks her to quit her job, but she cannot because it has brought her recognition, along with great self-respect, and she no longer is willing to adjust her life to the needs of the men in her life. Although Erin asks George to stay, he reluctantly leaves. Erin is angered when she learns that Ed has engaged a new partner, Kurt Potter, an expert in toxic cases, to work on the Hinkley litigation, but Kurt has given Ed a check covering all expenses to date. Later, Ed presents Erin with a check for five thousand dollars and buys her a new car. The case now has six hundred and thirty-four plaintiffs and Kurt devises a new legal strategy. Feeling that if they go to trial, PG&E could stretch out the matter with appeals for ten years or more, he recommends that they agree to binding arbitration whereby the case is heard only by a judge, whose decision is final and cannot be appealed. Erin reminds Ed that the residents are expecting a trial, but he agrees with Kurt. Erin, who feels that Ed is pushing her out of the case, has difficulties with Teresa, Kurt’s prim, condescending co-counsel, but surprises her with her knowledge of the plaintiffs’ backgrounds. Kurt tells Ed that they must establish that the PG&E head office knew that the water was bad prior to 1987 and did nothing about it. In order to use the binding arbitration strategy, it is necessary that ninety percent of the plaintiffs agree to it, so Ed addresses a meeting at the Hinkley community center and eventually convinces almost everyone that this is their best chance to get money needed to meet ongoing medical expenses. However, they are still about two hundred and fifty signatures short, so Erin stays in a nearby motel and goes door-to-door, seeking the additional signatures. She asks George to come there and look after the children and he agrees. One night, after securing a bartender’s signature, Erin is approached by Charles Embry, whom she thinks is trying to pick her up, but Charles tells her that he used to work at the plant and that his forty-one-year-old cousin has just died from cancer after working in the water cooling towers. Charles tells Erin that he was assigned to destroy a lot of documents, most of which were dull, but some of which were related to water readings in holding pools and test wells. After getting information from the documents that Charles did not destroy, Ed and Erin present Kurt with the necessary six hundred and thirty-four signatures plus incriminating memos from the PG&E head office to the Hinkley plant. Later, Erin and George return to Hinkley, and Erin takes him to meet Donna. Erin tells Donna the news that the judge has ruled that PG&E will pay the plaintiffs three hundred and thirty-three million dollars. She then tells the overjoyed and relieved Jensens that they will receive five million dollars. Back in the office, the still-contentious Erin is working on another case when Ed gives her a bonus check, but warns her that the figure is not exactly what they discussed. Erin is outraged that Ed is underestimating her value, but rendered speechless when she sees that the check is for two million dollars.