Matt Damon delivers an indelible, implosive performance in “Stillwater,” a deeply personal human drama disguised as a crime thriller.

The film opens in theaters this week after receiving a five-minute standing ovation at the Cannes Film Festival that brought the actor to tears.

Now 50, Damon sets aside the boyish charm that made him a star in 1997’s ”Good Will Hunting” (he and pal Ben Affleck won an Oscar for their script) and such blockbusters as the “Ocean’s” franchise, the Jason Bourne trilogy and his Golden Globe winning “The Martian.”

PHOTO: Matt Damon and Lilou Siauvaud in "Stillwater," 2021.
Focus Features
Matt Damon and Lilou Siauvaud in "Stillwater," 2021.

As Bill Baker, a widowed oil-rigger and ex-con from Stillwater, Oklahoma, Damon is barely recognizable. Thickly muscled under a beat-up cap, with a goatee and a clenched, “yes ma’am” politeness, this good ol' boy hides an intensity that makes him look coiled to spring.

Bill is a fish out of water in Marseille, the French port where this red-stater who didn’t vote for Trump only because a felony conviction forbade it, has come to visit his daughter, Allison (Abigail Breslin), five years into a nine-year sentence for a crime she says she did not commit.

Portrayed in the media as “that evil American lesbian” who murdered her French-Arab girlfriend, Allison keeps hitting legal obstacles she doesn’t trust the father who neglected her to surmount. It’s a plot that recalls the case of Amanda Knox, the American exchange student who spent four years in an Italian prison before being exonerated for the murder of her roommate.

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That “Stillwater” doesn’t degenerate into exploitative, true-crime trash is due to the artistry of director and co-writer Tom McCarthy, whose 2015 “Spotlight” won the Oscar for best picture. McCarthy guides Damon and a superb cast around corners you don’t see coming.

Chief among them is Bill’s touching relationship with single mom Virginie, beautifully played by “Call My Agent” star Camile Cottin. Virginie is a struggling stage actress who rents a room to Bill and helps him negotiate the byzantine French legal system while slowly letting him into the life she shares with her 9-year-old daughter Maya (a lovely Lilou Siauvaud).

PHOTO: Matt Damon in "Stillwater," 2021.
Focus Features
Matt Damon in "Stillwater," 2021.

With this new chance at love, Bill forms ties he never had with his daughter. In a delicate moment that speaks volumes, this makeshift family dances together to Sammi Smith’s “Help Me Make It Through the Night.”

If only. It’s crushing when Allison, who is allowed one day’s leave from prison, meets her father’s adopted family. Mostly sidelined by the script, Breslin seizes this chance to reveal the pain of a young woman whose life is more than question of guilt or innocence.

The film flirts with absurdity near the end when Bill feeds into the European cliché of an ugly American cowboy out to save the day. Luckily, Damon works hard to show that Bill is something more complex and feeling than a thug who’d quickly revert to violence to track down a suspect, Akim (Idir Azougli), who might clear his daughter.

Allison claims she saw it coming, that she and her father are fated to be forever screwups. But are they? The film is at its riveting best when it doesn’t try to tie up loose ends for this father who carries two guns but prays before every meal. Even when the final scene of this emotional powerhouse fades to black, “Stillwater” is only beginning to haunt your dreams.