“Everyone grieves differently,” says the pastor where services are being held for Brenda Arnaud at the start of Jim Cummings’ “Thunder Road. “There’s no right way or wrong way.” Still, Brenda’s son Jim (Cummings) tests that sanctity of that idea, which might not come as a surprise to anyone who previously saw Cummings’ Sundance Grand Jury Prize-winning short of the same name as his first feature, though it certainly startles those gathered to celebrate Brenda’s life. Dressed in his police uniform, Jim pays tribute to his mother, a dance instructor and certified public accountant (stressing “certified” as if it were an accomplishment on the level of the Nobel Prize), in an extemporaneous eulogy that includes digressions about girls he knew in elementary school and shoutouts to his alma mater (“Go Tigers!”) as a roundabout way of describing her charity. Those who wouldn’t know better might think he’s drunk, but rather than pushing away the pain, he feels things too intensely, whether it’s anger, anguish or happiness, and as the lone child of Brenda’s three to show up for her funeral, he’s frustrated in knowing in advance it’s all on him to deliver a proper send-off. After all, expressing himself accurately has never been his thing.

In the short, the memorial ends gloriously with an awkward dance set to the titular Bruce Springsteen song as an uncomfortable yet beautiful sacrifice in dignity to pay tribute to what he thinks his mom would’ve wanted. But in learning that life goes on for the tortured, yet well-intentioned Officer Arnaud, Cummings crafts something even more exquisite, giving Jim a daughter Crystal (Kendal Farr) to raise, creating questions for himself about how he should be a model for her and how having a mother as a primary parent after his dad left shaped him. After the funeral, things are not off to a good start when Jim is served with divorce papers from his ex Roz (Jocelyn DeBoer), who seeks full custody of Crystal before moving out of Austin to Tuscaloosa with her new boyfriend. He’s also aggravated his superiors at the police department by returning to the job too quickly, skipping the requisite week he was given to cool off with tensions flaring during a routine arrest. Left to himself, with as much help as he can get from his partner Lewis (Nican Robinson), Jim finds new ways to shoot himself in the foot with his quick temper and his lack of a filter to catch his darkest thoughts before they come out of his mouth.

Having played him previously, Cummings clearly knows Jim so well at this point that one would suspect he could place the character in any scenario and make it compelling since he’s so fully formed, with all of Jim’s minor tics perfectly performed and the realization setting in of how every single one is a manifestation of how he was brought up – the rationale to act without thinking a survival instinct from often feeling alone, but the quick apologies that come right after when he sees he’s in the wrong a product of the mother he described at the start of the film. He’s the last person you’d want with a badge and a gun since he doesn’t think things through, but at the same time, you understand he became a cop out of the same responsibility he shows throughout the film as others, seemingly more rational and stable, fail to show up at important moments at every turn.

There’s a genuine goodness that runs throughout “Thunder Road” that’s unusual to see anywhere, let alone in movies, as Jim does his best to do right and while he’ll often go to ridiculous lengths simply just to make peace with himself, every time he makes a little bit of headway, it causes the heart to swell. Cummings’ remarkable performance is central to keeping the audience so deeply invested, but as a director, he’s equally canny in bringing one closer to Jim, dispatching a brilliant score selectively for maximum effect, finding single instruments with rich interior sounds to express what’s stirring inside him, and using cinematographer Lowell A. Meyer’s beautiful camerawork to express emotional distance with frames that never look overly composed yet filled with depth. Production designer Charlie Textor also does an exceptional job of creating Jim’s life with the environments he steps foot in, where the warmth of his partner’s place can remind Jim of what he doesn’t have as a family man or knickknacks around his own spare home can feel special when his daughter is there to visit.

“Thunder Road” is that rarest of creatures, a truly moving drama with spikes of sharp humor that is so obviously the work of a singular artist that it’s exciting to think of what Cummings could do next. But for now, you’re just overwhelmingly grateful that he’s given the world something as personal, heartfelt and immensely entertaining as this. It’s a stunner.

“Thunder Road” will play at SXSW on March 13 at 12:30 pm at the Alamo Lamar D and March 16 at 9:45 pm at the Alamo Lamar B.