I’m hard-pressed to think of a screen role Aaron Eckhart didn’t commit to, heart and soul. A-pictures and B-movies, bit parts or leads, he’s present, prepped and accounted for every time somebody yells “Action!”

For his latest, he’s hit the gym, mastered a faint drawl and studied that confused, punch-drunk look of a veteran fighter whose memory and very consciousness comes and goes as he staggers towards 50. Stoop-shouldered, he leans so far into his gait that it’s like he’s stalking a foe, or about to fall down in the process. It’s a lovely, lived-in performance.

“Rumble Through the Dark” is a Bayou brawler noir, a film about a back alley fighter who never really “put on the gloves.” Anybody who keeps brass knuckles in his pocket isn’t a “boxer,” and probably never was going to be.

Jack Boucher’s last name isn’t the only source of his nickname. “The Butcher” the Cajuns and their neighbors call the guy with the French surname to suit his profession. Jack makes a mess out of his foes, except when he’s paid to take a dive. And even then, he makes a punishing show of it, making them pay to “fix” the fight.

Jack’s in hock to the madam and bookie they call Big Momma because of course they do. Marianne Jean-Baptiste, who broke through with Mike Leigh’s “Secrets & Lies” nearly 30 years ago, brings a world weary/worldwise menace to a character others speak of warily, as she has a habit of branding a “$” sign on those who owe her money.

Jack fights and he gambles. He wakes up and passes back out again. He’s spending an awful lot of time trapped in memories of childhood abandonment, experiencing flashbacks of the stepmother who took him in and who taught him to stand up to bullies with extreme prejudice.

In Louisiana, having a “lesbian mom” is going to get you teased. Got to be tough to deal with that.

Just as Jack thinks he’s going to get square with Big Momma thanks to a lucky turn or ten of the roulette wheel, he loses the cash. Annette the Tattoo’d (fleshy, inked-up Bella Thorne) lady in a traveling carnival is the one who finds his winnings.

Filmmaking siblings Graham and Parker Phillips take their movie’s sweet time getting the carny with the cash and “lots of questions” in the same truck with the bloodied, broke brawler who might have the answers.

Yes, their picture dawdles. They give screen time for supporting players like Ritchie Coster, as Baron, who runs the seedy carnival, Mike McColl as a greedy carny/mechanic and Christopher Winchester, as Big Momma’s muscle, to make their marks.

And they give Jean-Baptiste almost all the best lines.

“I wish you knew how bad I wanna put you outta your misery.” Fight or don’t fight. You might get hurt if you do, you WILL get hurt if you don’t.”

“I can’t figure out whether you’re gettin’ braver or dumber.” To her, he’s just a guy prone to “rumble through the dark, chasin’ something he ain’t never gonna catch.”

The Phillips (“The Bygone” was theirs) allow director of photography David J. Myrick the time to light for mood — gloom, poverty, downmarket despair — and compose one immaculate shot after another. This modestly-budgeted indie is so gorgeous to look at you hope Martin Scorsese doesn’t see it. “Killers of the Flower Moon” has the air of a movie shot on a cell phone by comparison.

That “dawdling” thing gets in the way of this simple, sometimes trite and even corny narrative. This is a B-movie by genre — a “Big Fight” picture — by tropes and by design. Yet the Phillips never let a single spare scene get across a plot point when five long, often wordless and evocative ones will do.

But it’s never less than watchable. And Eckhart rewards the obvious care and time it takes to make a film look this polished, gritty and immersive by giving these young filmmakers every penny’s worth in every take. Thorne makes the most of a role that’s downmarket, but sentimental.

And Jean-Baptiste takes a stereotypical character and makes her pop off screen, playing a woman with agency, an eye for spectacle, an unforgiving streak and a branding iron she’s not shy about heating up when the need or the sadistic urge arises.

Rating: R, grisly, graphic violence, profanity, smoking

Cast: Aaron Eckhart, Bella Thorne, Ritchie Coster, Christopher Winchester, Mike McColl and Marianne Jean-Baptiste.

Credits: Directed by Graham Phillips and Parker Phillips, scripted by Michael Farris Smith. A Lionsgate/Screen Media release.

Running time: 1:54