Folding sexual arousal and religious ecstasy into a single, gasping sensation, “Saint Maud,” the feature debut of the director Rose Glass, burrows into the mind of a lonely young woman and finds psycho-horror gold.

Maud (a mesmerizing Morfydd Clark) is a live-in palliative care nurse in an unnamed British seaside town. A recent religious convert — we don’t know why, but the film’s unnervingly gory opening more than hints at a profound trauma — Maud believes that God has chosen her to guide the fallen to salvation. This mission leads her to the forbidding hilltop mansion of Amanda (Jennifer Ehle), a celebrated dancer and choreographer now stricken by late-stage lymphoma.

The ensuing interplay between caregiver and patient, faith and denial, asceticism and intemperance, veers from chilling to morbidly comic. Determined to enjoy her final few weeks, Amanda submits to Maud’s prayers while remaining an enthusiastic hedonist. Smoking and drinking with relish, hosting gatherings of her bohemian friends and romancing a younger lover (Lily Frazer), Amanda nevertheless finds comfort in the intimacy of Maud’s quiet ministrations. Still, Maud is a mystery (for one thing, as we learn late in the film, her name isn’t really Maud), but whether she is a batty Bible-thumper or something infinitely more sinister, we have barely 84 minutes to find out.

Using every one of them, Glass leans heavily on a hermetic atmosphere humming with zealotry and barely suppressed lust. Drifting into trances and bedeviled by fiery stomach pains, Maud nurtures a piety that seems never less than a burden. In one unsettling sequence, she wanders past the town’s rundown arcades and into a bar, her desperation for company overwhelming her disgust at her own needs. But there’s a price, as the raised red welts on her pale body bear out: Passion for anyone but Christ must be punished.

“May God bless you and never waste your pain,” she tells a beggar, perhaps indicating concern that her own agonies are being squandered. And while the film’s graceful special effects leave space for more than one reading of Maud’s actions — an ambivalence that’s most pronounced in the gorgeous, hallucinatory finale — it’s clear she’s on a fixed trajectory, one that promises a Grand Guignol climax to her seeming delusions.

Formally controlled and visually elegant, “Saint Maud” has a dark, spoiled beauty and a shifting point of view that questions Maud’s distorted vision. Favoring suggestion over specifics, the script (also by Glass) doesn’t always avoid the familiar potholes of the genre: the nosebleeds and Gothic interiors, the baleful lighting and self-harming behavior. Gestures toward Maud’s troubled past remain vague, but the movie’s artistry and sensuality suck you in. Maud knows she can’t save Amanda’s body; what she wants is her soul.

Saint Maud
Rated R for lethal scissors and loony spirituality. Running time: 1 hour 24 minutes. In theaters. Please consult the guidelines outlined by the Centers for Disease Control and Prevention before watching movies inside theaters.