An unlikely romance, played out against a background of violence, is the focus of “Beast.” Set apart from similar pictures by its unusual locale, the Isle of Jersey (with its historical blend of French and English culture), and fierce lead performances by Jessie Buckley and Johnny Flynn, Michael Pearce’s debut feature maintains an unsettling mood until it arrives at a grimly shocking conclusion. In the end, the degree of psychological insight it offers is negligible, but along the way it will keep you intrigued.

Buckley anchors the film as Moll Huntington, the younger daughter of uptight, rigid Hilary (Geraldine James, appropriately snooty and condescending). Moll seems completely under her imperious mother’s thumb, but beneath an appearance of submissiveness she has a tortured history involving an act of violence when she was bullied at school, and she harbors a rebellious streak, When her elder sister Polly (Shannon Tarbet) steals the attention at Moll’s big birthday party by announcing her pregnancy, Moll sneaks off by herself. She winds up at a raucous club on the beach, where she spends the night dancing with a stranger and goes off to the beach with him. His intentions are hardly gentlemanly, though, and fortunately for Moll, she’s rescued from his clutches by the intervention of brooding petty criminal Pascal Renouf (Flynn), who identifies himself, only half jokingly, as the descendant of a Norman culture whose territory the English have usurped.

Pascal is a scruffily handsome handyman, but he’s also a poacher and general n’er-do-well, and as Moll latches on to him, Hilary is horrified. Pascal, as it turns out, is also a suspect in a series of murders of young women on the island, a fact impressed on Moll by Clifford (Trystan Gravelle), a local detective who’s obviously infatuated with her himself. But Moll responds to their warnings by getting even closer to Pascal, and her initially reserved persona crumbles under his rugged influence.

But there is a shadow over their relationship: the murder investigation. (That aspect of the plot is inspired by the case of Edward Paisnel, the so-called Beast of Jersey who terrorized the island in the 1960s.) Moll is pressured by the authorities to retract the alibi she persistently gave to Pascal for the night on which they’d met, claiming falsely that he was the man she’d been dancing with all night—a night when another girl was killed. She holds to her story steadfastly, though she begins to have doubts after his violent nature surfaces when she confronts him with her suspicions. They don’t abate even after another man us arrested as the culprit.

“Beast” concludes with the final revelation of the truth about the murders, but it leaves open the question of who the true beast in the equation is, because throughout it is Moll who registers the greatest animal power, not only in her confrontations with the police but elsewhere as well. When accosted by town thugs when she insists on attending the funeral of a murder victim, she turns on her pursuers and shrieks at them with a fury that sends them fleeing. She crawls into the hole where the girl was buried and burrows in the dirt. And when the truth of the killings comes out, it is her ferocity that explodes.

Pearce’s touch isn’t always faultless in “Beast.” Some of the lines of dialogue are leaden, and the narrative opacity, accentuated by Mays Maffioli’s deliberate editing, while ordinarily fascinating can sometimes be taken too far. But he secures remarkable performances from Flynn, James and especially Buckley, who fills Moll with a venomous, simmering rage that the film can barely contain. With a bevy of excellent supporting turns and cinematography by Benjamin Kračun that gives the Jersey locations a rough, vaguely menacing ambience, he’s pulled off a strangely compelling portrait of a misbegotten romance between two troubled outsiders struggling against the demands of the peculiar society in which they were born. That it’s also a murder mystery of sorts is an added bonus that adds malignant flavor to the dark, twisted tale.