4 stars

Based on the true story of one lawyer's tenacity in exposing the damage done by corporate greed, director Todd Haynes (Carol) finds a way to make the world of plaintiffs, legal procedure and complex chemicals fascinating - thanks to some excellent screenwriting and a riveting performance from Mark Ruffalo.

Ruffalo plays Cincinnati lawyer Robert Bilott, who is accosted by Appalachian farmer Wilbur Tennant (Bill Camp) to do something about the strange deaths of livestock occurring on his property in Parkersburg, West Virginia.

Tennant is adamant that the problem lies with the large chemical company, DuPont, which not only acquired the neighbouring farm for landfill, but which also "owns" the town. Asking too many difficult questions about DuPont in Parkersburg seems to make enemies quickly.

Reluctant to get involved because he specialises in defending chemical companies, Bilott nevertheless decides to do the right thing, and takes a trip to visit Tennant. Mad cows and the blackened teeth of children are enough to convince him that something's afoot.

He starts investigating, making discreet enquiries through colleague Phil Donnelly (Victor Garber), a lawyer with DuPont who is initially sympathetic.

But as the case gets murkier, it becomes clear Bilott going to have to go head to head with the powerful chemical giant, a task utterly opposed by most of his fellow partners and his wife Sarah (Anne Hathaway). Fortunately, Bilott has the support of his long-suffering and ethically minded boss Tom Terp (Tim Robbins), who realises that the firm's reputation is more important than the potential revenue stream.

Writers Mario Correa and Matthew Michael Carnahan (World War Z, The Kingdom) cleverly minimise the legal exposition. They package the narrative initially as an investigative mystery, drawing the audience into the fascinating - and disturbing - world of chemical experimentation and corporate cover-up.

Then, when the battle lines are clearly drawn, it becomes a David and Goliath story, with Ruffalo doing the emotional heavy lifting. Director Haynes understands that it's Bilott's insider perspective that gives the story its dramatic complexity: he's a man who is already living in the belly of the beast.

The story is adapted from a New York Times article, The Lawyer who became DuPont's Worst Nightmare by Nathaniel Rich, with Bilott clearly portrayed as quiet, thorough and tenacious.

Ruffalo's great skill here is building a cinematically compelling character without compromising those virtues. He's the story's everyperson, the stand in for the viewer, discovering the dreadful facts and guided in his actions by his unwavering conscience.

Camp turns in a great supporting performance as the barely understandable and highly emotional victim, and it's only Hathaway who seems out of place in the film, her portrayal of Sarah lacking much depth.

Although the film is mostly set from 1998 onwards, there's a strange opening scene, perhaps more in keeping with some of Haynes' quirky past movies. It's 1975 and three teenagers are running through the dark to take a dangerous naked swim in a lake that's protected by a wire fence.

While Haynes creates a link to the rest of the story, the mood and year of the scene make it feel like a reference to the opening of another film about ordinary people versus a monster: Jaws.

Although the film runs a little over two hours, Ruffalo's presence, and the sheer incredulity of the scale of this scandal, will keep you firmly in your seat.