“Never waste your pain” Maud (Morfydd Clark) advises, her voice rarely rising above a whisper, even in voiceover. A devout palliative nurse with quite a bit of emotional baggage, Maud searches desperately for meaning. More often than not, she finds that meaning in her own pain; pain suffered in the name of God. With Amanda (Jennifer Ehle), an ex-dancer knocking on the doorstep of the afterlife, she just might have found her purpose on this earth: to redeem and purify. Saving a soul proves nasty business, especially as intimate personal relationships blossom, but Maud will stop short of nothing to do just that, consequences be damned.

In the electrifying and thought-provoking feature debut from Rose Glass , human holiness is a disease. Not unlike addiction or mental illness, the reality distortion that Maud suffers is palatably off: her “connection to God” is not one of blind faith but of direct call and response. In Maud’s mind, God communicates with her openly; Zooming in for a quick chat and a bit of direction.

The hubris of Maud is an early warning sign that something is very, very wrong. We see Maud tremble as a force she describes as “God” touches her, inflicting orgasmic shivers, her eyes rolling back in her head in pure ecstasy. But not all things in this spiritual relationship are so pleasant and Maud turns to her own suffering and self-flagellation whenever she disappoints her Holy Savior. In this sense, devotion is explored as a vehicle for body horror as Maud burns herself, stuffs nails into her shoes, and otherwise inflicts corporeal pain to beg penance, all the while calling her own devotion into question. The body horror elements are gnarly, evocative of The Passion of The Christ and The Exorcist both.

Clark is excellent in the role: withdrawn, soft-spoken, and harboring some deliciously dark secret that lies just offscreen. There’s a caged feral enthusiasm within Maud that’s hinted at, particularly through conversations with her old nursing colleague Joy (Lily Knight), but Clark masterfully contains it, allowing Maud’s shifty nature to peek through without being overly-showy about it. To her, the shutters and direct communion with God are symptoms of a soul offering itself to some kind of higher power but we’re left to wonder what nefarious alternative might be at play. Maud may have herself convinced that Amanda is the one in need of saving but we know the opposite is clearly true.

Clark’s chemistry with Ehle provides the foundation and emotional crux of the film: the would-be savior and the former dancer suffering through the final stage of spinal lymphoma. A bitter woman, lacking in faith but with a hidden tender side that’s occasionally carved open by a notable cruel streak, Amanda tests Maud’s inner conflict, teasing the central premise of whether Maud is undergoing a spiritual breakthrough or simply a mental breakdown.

Writer-directer Rose Glass delivers on just about every level, ushering out solid performances in service of a slow burn that erupts into a roaring conflagration by the end. Moody and uncanny, our mind is never allowed to stray far from the fact that something is seriously off. That the film is set in the U.K.’s Coney Island knockoff, complete with rigged carnival games, tacky rides, cheap overstuffed prizes, and slabs of fried dough in various forms, hints at another side of Maud, as does the all-too-brief prologue; a blood-stained glimmer of some obscured tragedy. But however vibrant and omnipresent that pain that may be, Maud has channelled it into purpose. In service of the higher storytelling gods, Saint Maud cautions against the presumption of assigning pain purpose, particularly when all is not right upstairs.

CONCLUSION: Expertly building suspense and tension – and popping that bubble perfectly with some of the most effective jump scares of recent memory – ‘Saint Maud’ has all the markings of a horror great, with a killer ending to boot.