Erin Brockovich (JULIA ROBERTS) is a down on her luck single mother who's now twice-divorced. With two young children, Matthew (SCOTTY LEAVENWORTH) and Katie (GEMMENNE DE LA PEŅA), along an infant to care for, but no prospects of employment, Erin doesn't think things could get worse, but she's then hit by a car.
While her ensuing court case doesn't result in a settlement - partly due to her "earthy" demeanor and language - she does eventually persuade her attorney, Ed Masry (ALBERT FINNEY), to give her a job as a filing clerk. Although that demeanor and her suggestive attire don't sit well with the small law firm's more conservative workers, Erin's happy to have a job, as well as a new boyfriend, George (AARON ECKHART), her Harley-riding, new next-door neighbor who gets along tremendously with her kids.
While working on a pro bono real estate case, Erin uncovers some medical files mixed in with the rest and convinces Ed to let her further investigate the matter. As a result, she discovers that the small-town residents of Hinkley, including Donna Jensen (MARG HELGENBERGER), have seemingly been poisoned by contaminated ground water caused by the local Pacific Gas and Electric plant.
Despite Ed's credible worries that their small firm could never battle a multibillion-dollar corporate behemoth like PG&E, Erin continues on her crusade to interview as many of the local townsfolk as possible. As she uncovers ever more victims of the illegal dumping of an incredibly toxic and carcinogenic form of chromium, Erin and Ed, along with some late in the game legal assistance by Kurt Potter (PETER COYOTE) and his assistant, Theresa Dallavale (VEANNE COX), prepare to battle the corporate giant and its legal team over damages due to the residents of Hinkley, all while risking everything dear to them.