In ‘Dark Waters,’ Mark Ruffalo scores as another kind of avenger: an underdog lawyer

Mark Ruffalo is a master at playing a certain type of earnest character who often wears a quizzical expression — not because he’s slow on the uptake, but because he’s the smartest person in the room and he has questions no one else has even thought to ask.

Characters such as the Pulitzer Prize-winning investigative journalist in “Spotlight”; the San Francisco police detective who figures out subtle ways to feed information to a free-lancer in “Zodiac,” even Dr. Bruce Banner in the “Avengers” movies.

As a crusading attorney in “Dark Waters,” Ruffalo has a role squarely in his comfort zone, and it’s no surprise he knocks if out of the park in a true-life David v. Corporate Goliath legal thriller with echoes of films such as “A Civil Action” and “Erin Brockovich.”

Ruffalo’s Robert Bilott isn’t the kind of guy who’s going to punch out the villain or give one of those grandiose, theatrical courtroom speeches we see in a John Grisham movie.

He’s a noble pest. He’ll attend a fancy fundraiser just so he can corner the powerful executive who’s been dodging his calls. He’ll quietly but firmly stand up to the partners at his law firm who want him to drop a controversial case. He’ll knock on doors, he’ll make cold calls, he’ll forgo sleep, he’ll rattle cages, he’ll outwork you and he’ll outlast you.

Directed in a relatively straightforward style by the usually quirky, indie-leaning Todd Haynes (“Safe,” “I’m Not There,” “Carol,”), “Dark Waters” isn’t as flashy or as shamelessly audience-pleasing as “Erin Brockovich.” Ruffalo doesn’t get Oscar-bait speeches in which he rattles off personal details about the “little people” he’s representing, followed by Oh, snap! personal insults.

But Robert is every bit as determined as any underdog attorney in recent movie history. Over the course of a dozen years, he puts his career in jeopardy, he works so hard he literally has a stroke and he almost loses his family as he refuses to surrender in a seemingly unwinnable battle against the mighty and deep-pocketed DuPont company.

It all starts with one Wilbur Tennant, a West Virginia farmer who is convinced DuPont has literally poisoned his cattle, his land — and maybe his family as well.

The great character actor Bill Camp plays Wilbur, who speaks with such a heavy-accented growl we almost need subtitles to understand him. Wilbur stomps into the offices of the Cincinnati law firm where Robert works, hoping Robert will represent him because Wilbur is acquainted with Robert’s grandmother — who lives in the same depressed, working-class West Virginia town where Robert grew up.

Robert explains he can’t take the case. Yes, his firm specializes in environmental law, but they’re all about DEFENDING the big-time corporations. (In fact, they’re hoping to land Du Pont as a client.)

Yeah, but Grandma…

Robert loves Grandma, and that’s enough to guilt him into paying a visit to Wilbur’s farm to check out Wilbur’s claim DuPont has dumped toxic chemical waste into the Dry Run Creek where his animals drink.

He’s horrified to see evidence of animals born with gruesome birth defects. He’s stunned to learn Wilbur has had to bury more than 100 cattle that have died prematurely. He’s taken aback to see Wilbur’s daughters have blackened teeth — possibly caused by tainted tap water. Wilbur himself has cancer, and he’s hardly the only local (including dozens of former DuPont employees) who has been struck with serious and often fatal illnesses.

It becomes clear DuPont has knowingly exposed thousands if not millions of consumers to dangerous levels of toxins — but every time Robert gets close to proving his case, he’s thwarted by DuPont’s vast resources and an army of attorneys willing to delay the case for as long as it takes, not to mention the corporate-friendly scientists who testify in DuPont’s favor, and the members of his firm who are growing increasingly resentful of a crusade that’s alienating the very type of clients they want to represent.

Anne Hathaway does fine work in the obligatory Supportive but Long-Suffering Wife role. We know it’s only a matter of time before she gives the speech about how Robert is never there even when he’s there, and he’s more concerned about the families he represents than the family right there at the dinner table.

Tim Robbins has a more nuanced role as Tom Terp, the senior partner at Robert’s silk-stocking law firm. We expect Terp to order Robert to either drop the case or turn in his resignation, but he shares Robert’s moral outrage and supports him — at least to a point.

“Dark Waters” is based on the 2016 New York Times Magazine article “The Lawyer Who Became DuPont’s Worst Nightmare,” which chronicles a case that stretched on more than a decade. Director Haynes is almost too faithful to the timeline, resulting in some lulls in momentum, especially in the middle third of the story.

Of course, we know Robert will win the day. They don’t make movies about crusading attorneys who get crushed in court by corporate monoliths.

Besides, that’s Mark Ruffalo. He’s a champion at playing guys who prove slow and steady wins the race.