Saint Maud is one of those films that will confound you and disturb you while you’re watching, and then haunt you before you even have time to get cocky enough to congratulate yourself for surviving. It is not the kind of horror film that’s going to frighten you. There are no cheap jump scares, no triggering gore. It is simply chilling.

Maud (Morfydd Clark) is a fervently if newly pious woman whose belief bleeds into her work as a hospice nurse. New client Amanda (Jessica Ehle) is a former dancer currently dying of cancer. For the most part they get along but visits from Amanda’s lover Carol have Maud fearing for Amanda’s very soul (which is a matter of some urgency, if it’s not too crude to say). Maud has only recently turned devout (some trauma is vaguely hinted at), and is now of the certain belief that humanity is amoral, lustful, and terribly wicked and needs very badly to be saved. And since God has ever so kindly and every so explicitly told her that He has very special plans for her, Maud connects the dots and finds that perhaps she is meant to be its saviour.

What’s the difference between religious fanaticism and mental illness? Maud’s zealotry is depicted as a compulsion, indeed an obsession. She feels it necessary and right, but there is a gulf between what she believes and what others believe – Amanda specifically, though clearly not solely. However, writer-director Rose Glass leaves a little wiggle room for doubt. Is it possible, is it just the slightest bit possible that God really is speaking to Maud?

Part horror, part psychological thriller, part character-driven drama, Saint Maud can be read in a variety of ways and this expert ambiguity is the film’s coup de grace. Glass has the temerity to respect Maud either way; this dignity, this refusal to dismiss her, is bold and singular. Whether miracle or mental breakdown, Maud is entitled to compassion, which makes Glass’s film all the more deliciously vexatious.

Clark gives a stunning, visceral performance. The story is told almost entirely from her perspective, so where one might see delusion or psychosis, Maud sees only signs from her God, and burning bushes. It’s convincing and disorienting yet Glass always plays it both ways, like that picture of the animal that’s either a rabbit or a duck, depending on how you’re looking at it at any given time. While the intention may be shrouded, Saint Maud is still a deeply satisfying not to mention profoundly atmospheric piece of cinema that’s either supernatural or a psychotic break, and I don’t even care which. It is fascinating, carefully crafted, thematically complex, and fantastically unsettling.

Saint Maud will be available digitally and on demand in North America February 12 2021.