By Derrick Bang | December 13, 2019 | 2:01 PM

When corporate attorney Robert Bilott (Mark Ruffalo, right) reluctantly visits the cattle ranch that has been in Wilbur Tennant’s (Bill Camp) family for generations, they’re startled by the sudden appearance of a heifer that appears to be viciously rabid. Courtesy photo

‘Dark Waters’

Four stars

Starring: Mark Ruffalo, Anne Hathaway, Bill Camp, Tim Robbins, Bill Pullman, Victor Garber, Kevin Crowley and Mare Winningham

Rating: PG-13, for dramatic intensity, disturbing images and brief profanity

Strong performances highlight this fact-based shocker

Mark Ruffalo has become this generation’s Henry Fonda. Or Jimmy Stewart.

Ruffalo’s performances radiate the same intelligence and integrity. The same resolute dedication to a cause. The same anguish at the realization that greed and cowardice too frequently trump benevolence and compassion. The same disbelief over the ease with which people in power feel no remorse overlying, cheating and ill-treating those less equipped to fight back.

The primary difference is that Fonda and Stewart mostly played fictional characters in their iconic films, such as “The Grapes of Wrath” and “Mr. Smith Goes to Washington.” Ruffalo takes it a step further, tackling actual individuals in an expanding roster of fact-based sagas that qualify as searing advocacy cinema.

He earned his third Academy Award nomination for 2015’s “Spotlight,” while portraying Pulitzer Prize-winning Boston Globe reporter Mike Rezendes, who led the investigative charge that exposed the local Catholic Archdiocese’s cover-up of child molestation cases. The film deservedly won that year’s Best Picture Oscar, and the viewing experience is jaw-dropping, as Rezendes and his fellow reporters uncover proof of the church’s ever-more-heinous behavior.

“Dark Waters” is even harder to watch.

Much harder.

This new film, also lifted from headlines, depicts defense attorney Robert Bilott’s heroic determination — over the course of two decades — to force DuPont to reveal that it had knowingly poisoned people for even longer. And not only had concealed such monstrous behavior, but defiantly maintained that it had done nothing “legally wrong,” and therefore could not be “blamed” for anything.

That last little detail comes well into a saga that already has become grim viewing. Director Todd Haynes’ approach is methodical and relentless, carefully fueled by the strong character dynamics that he delivered in “Far from Heaven,” “Carol” and other previous films.

The information dump is considerable but not insurmountable. In effect, we gradually learn the degrees of DuPont’s perfidy along with Bilott, while he becomes a reluctant investigator in the mold of Rezendes and — reaching further back — Bob Woodward and Carl Bernstein, in “All the President’s Men.”

Or, more closely linked, Erin Brockovich, in the 2000 drama named for that similarly righteous crusader. That case also started with water.

These events are grounded by Ruffalo’s quietly heartfelt portrayal of Bilott: a man not given to operatic speeches or useless explosions of rage, but rather a frequently silent observer of human nature, who goes with his gut when he senses something is amiss.

And who also possesses superhuman patience, while “working the problem.”

Matthew Michael Carnahan and Mario Correa’s mesmerizing script is lifted directly from Nathaniel Rich’s equally absorbing January 2016 New York Times Magazine article, which profiled Bilott at the moment of (apparent) long-awaited triumph. (The parenthetical is necessary. DuPont still hasn’t quit.) Carnahan and Correa didn’t need to embellish or make stuff up to heighten the drama; the plain facts are fascinating — and horrible — enough on their own.

Bilott meticulously exposed evil to a degree that too frequently defies description. We can’t help feeling a sick ache when being reminded of the U.S. Supreme Court’s 2010 Citizens United decision — along with other similarly misguided verdicts — which effectively determined that “corporations are people.” If so, history’s Mengeles, bin Ladens, Neros, Torquemadas and Borgias have nothing on DuPont.

The sidebar irony is that Bilott, as introduced, seems the least likely candidate for such a career-defining cause.

The story begins in 1998, when he’s approached by Wilbur Tennant (Bill Camp, salt-of-the-earth perfection), a feisty cattle farmer in Parkersburg, W.Va. His cattle have been dying by the score, and he’s convinced the cause is the massive landfill immediately adjacent to his property, where DuPont has been dumping unspecified waste from its nearby Washington Works plant. The two properties share a creek, from which Tennant’s cattle drink: water now visibly contaminated by grotesque liquid waste.

The farmer initially gets a hearing only because Tennant knew Bilott’s grandmother; he plays the “do a favor for a family friend” card. But Tennant doesn’t realize that Bilott is the wrong sort of attorney; as a newly minted partner at Taft Stettinius & Hollister in Cincinnati, Ohio, he has specialized in defending large chemical companies.

Tennant, too angry and stubborn to care about such technicalities, nonetheless makes an impression. Bilott visits the ranch; he watches the grainy videotapes the farmer has made of his own amateur dissections … because no local veterinarian will give him the time of day. Indeed, Tennant has been dissed by Parkersburg’s journalists, lawyers and politicians. It’s a company town. DuPont owns it.

Bilott cannot ignore the evidence of his own senses; he knows something is seriously wrong. Perhaps naïvely, he initially touches base with upper-echelon DuPont executive Phil Donnelly (Victor Garber), with whom he has a cordial professional relationship. Something seems to be amiss here, Phil; perhaps you could help me look into it?

Quite a few smarmy individuals parade through this chronicle, as it develops, but none is more unctuously condescending than Garber’s handling of Donnelly. Affability soon yields to furious contempt in a moment so explosive that we scarcely can credit it; Ruffalo’s shocked bewilderment mirrors our own.

When forced to respond, DuPont pulls the usual corporate trick of drowning Bilott in paperwork, hoping he’ll give up and go away. The mountains of boxes, all containing disorganized documents, seem a hopeless challenge. We cheer as Ruffalo’s resolute gaze tackles this problem the only way possible: one page at a time. (Rich’s article cites “more than 110,000 pages.”)

And herein lies possible salvation … because DuPont has been foolish enough to include confidential studies by its own scientists, going back half a century.

Much of which concerns an undefined something-or-other known only as PFOA, or C8.

Although essentially forced to work this case as a one-man operation, Bilott has allies. First and foremost is Thomas Terp (Tim Robbins), his Taft supervisor. At first blush the last person who’d ever tolerate or encourage such an obviously foolish endeavor, Terp nonetheless shares Bilott’s intrinsic understanding of right vs. wrong. Robbins gets a bravura moment, midway through the film when Terp angrily chastises Taft partners who argue that this “mission” will cause other corporate clients to flee.

It’s a pure cinematic moment. And if the actual Terp didn’t express himself as eloquently or passionately as Robbins, well, he should have.

Kevin Crowley is affably soft-spoken as Larry Winter, a West Virginia lawyer who abandoned his corporate origins to start his own personal injury practice, and who becomes Bilott’s eyes and ears in Parkersburg. Bill Pullman comes into the story later, as homespun, small-town attorney Harry Dietzler; Pullman’s performance is aw-shucks jovial, in the disarming manner that makes him dangerous to opponents foolish enough not to take him seriously.

Kelly Mengelkoch makes the most of her fleeting third-act appearance as a hissably vile doctor whose testimony is fully bought by DuPont at a key moment.

Anne Hathaway, somewhat distractingly looking like Jackie Kennedy, plays Bilott’s lawyer-turned-housewife, Sarah. She’s hard to read at first; although the actual Sarah acknowledged (in Rich’s article) the stress this case eventually put on their family, Haynes and his scripters initially put too much emphasis on this marital strife. Only later, once Hathaway has enjoyed her own “pure cinema” moment, do Sarah’s character and behavior become more reasonably balanced.

Ruffalo’s never-say-die handling of Bilott is the only thing to which we can cling, as this saga becomes progressively worse. Every time we think he has plumbed the depths of DuPont’s insidious behavior, the corporation makes an even more heinous move. And we wonder at this depth of closed-ranks malfeasance; was nobody willing to turn whistle-blower?

Apparently not.

“Dark Waters” should be required viewing in universities, communities and all levels of government bodies. Among its most powerful talking points — and they’re numerous — we’re left to ponder the ironic uselessness of “self-regulation.”

Along with a highly disturbing descriptor — “forever chemicals” — and its implications, moving forward.

You’ll not forget this one any time soon.