A Prayer Before Dawn is a film of few words and many, many, many punches. Jean-Stéphane Sauvaire’s prison drama is a portrait of aggro rage flailing about in search of a target, set in one of the least hospitable places on the planet. It’s an enraged whirling dervish of a character study, all fiendish fury and self-destructive desperation, driven by a star performance that’s intense to the point of madness, shot in an actual Thai penitentiary, and populated by legitimate—and legitimately scary—inmates. It’s as angry, unsentimental, and bracingly real as redemption stories come.

An adaptation of Billy Moore’s 2014 memoir of the same name, Sauvaire’s film (in theaters August 10, and available now on DirecTV) is a story of drug addiction, incarceration, and Muay Thai boxing in Thailand’s Klong Prem Central Prison, aka the “Bangkok Hilton,” a notorious maximum security facility filled with not-very-nice men. It’s there that Billy (Black Mirror’s Joe Cole) lands after his wayward life of underground fighting and drug-dealing (and abuse) leads to arrest. The specifics of his bust are left deliberately vague by the director; one moment he’s slinging in a bathroom, the next he’s trying to hide his stash up his ass as the cops burst into his apartment. Such whiplash-inducing confusion and bedlam is central to A Prayer Before Dawn, which at every turn is about conveying the runaway-train condition and circumstances of its protagonist.

From the initial sight of Billy getting massaged before a fight (and taking a hit of heroin), to his detainment and incarceration at Klong Prem, Sauvaire—delivering a worthy follow-up to his 2008 African-child-soldiers feature Johnny Mad Dog—dramatizes his action with next to no dialogue, few professional actors and even less context. It’s an approach that mirrors Moore’s bewildered headspace: he’s either overly aware of (and prone to explode at) everything, or enveloped in a narcotic trance. Attuned to its main character’s state of being, the director’s aesthetics marry urgent handheld camerawork to a phenomenally immersive audio design, such that everything sounds terrifyingly crisp and chaotic, or—after another dose of drugs—dull and distant, save for Moore’s heavy breathing and random nearby noises. That Nicolas Becker’s tonal score is mostly heard during those latter instances only further creates a striking stylistic dichotomy. For Moore, everything is 100 mph or hazy.

Though he’s the only white man around, Cole embodies Moore as an individual devoid of fear or self-control, and his hair-trigger temper makes A Prayer Before Dawn feel like a companion piece to Nicolas Winding Refn and Tom Hardy’s Bronson, another portrait of a burly Brit with fisticuffs constantly on his mind. Moore arrives at this institution a feral beast, and it’s not long before his unbridled behavior gets him thrust into a solitary confinement cell so small he can’t even stand up, and then relocated to dingy barracks (where prisoners sleep shoulder-to-shoulder on floor mats) filled with criminals covered head-to-toe in tattoos. These characters are played by many men actually serving time in Thailand, and their authenticity is unmistakable. They’re terrifying psychos prone to out-of-the-blue outbursts, as when, in the film’s most harrowing scene, they hold Moore at knifepoint and make him watch them rape a weak inmate against a wall—an assault that results, the next morning, in the victim’s suicide.

Moore exists, moment to moment, on the razor’s edge of restraint (and sanity), and Sauvaire conveys his frightening disorientation by regularly refusing to subtitle Thai speakers’ comments. He also maintains close proximity to Cole, the better to capture the barely-suppressed savagery burning in his eyes (save for when smack lulls him into a blissful stupor). That’s even more true once Moore heads to the gym and, shortly thereafter, nets an initial fight which the director stages in a single take that’d make Creed’s centerpiece blush. Dropping viewers suddenly into the final few seconds before the fourth round begins, and situating his camera up against his pugilistic subjects as they trade furious blows for minutes on end, Sauvaire dispenses with hand-holding and subtlety as he depicts this skirmish in all its brutal glory. If there’s choreography to this blistering Muay Thai barrage of fists, knees and feet, I couldn’t see it.

A Prayer Before Dawn barrels forward, refusing to sentimentalize any particular incident or Moore’s overall plight. It’s a descent into a hell populated by demons ruled by vicious impulses, and Cole proves a magnetic tour guide through these shocking environs. His oft-shirtless body a block of sweaty muscle, the actor is genuinely unhinged throughout, all while locating the glimmers of humanity still present, however faintly, inside Moore’s wild heart. A relationship with a trans woman named Fame (Pornchanok Mabklang) proves a fleeting respite from Moore’s day-to-day insanity. Yet he remains a powder keg ready to erupt, and Cole’s lack of interest in softening his characterization—by, say, trying to make Moore seem like a good guy who could just use some TLC—gives the action a rugged realism. He’s a caged animal looking for an outlet, any outlet, for his wrath and misery, as well as, ultimately, a way to harness those emotions before they lead to doom.

“I need to fight,” says Moore, and he finds salvation via boxing after he’s relocated to a new cell full of fellow combatants who—along with a chain-smoking trainer—take him under his wing, providing him with the support and tutelage his untamed soul requires. Not that transformation and transcendence come easy in A Prayer Before Dawn. Sauvaire’s climax involves Moore literally fighting for his life, thanks to an internal rupture that will kill him should he receive more blows in the ring, and gangsters who threaten him with injections of AIDS-contaminated blood should he lose his tournament match (and thus cost them gambling winnings).

That final bout is a flurry of limbs that crescendos with borderline-unbearable tension, beginning as a grave attempt to survive and ending as a cathartic release. Even then, however, Sauvaire doesn’t pull at one’s heartstrings. Instead, he allows his gritty material to speak for itself, right up to a silent last sequence in which Moore achieves a measure of understanding, acceptance and true strength by coming face-to-face with his past—and, by extension, himself.