A devoutly Christian nurse becomes obsessed with saving the soul of her patient in Saint Maud. Maud (Morfydd Clark) is a young nurse, who arrives to give palliative care to cancer-ridden ex-dancer Amanda (Jennifer Ehle). Having recently discovered religion, Maud is constantly praying to God for guidance in her life. After observing Amanda's sinful behaviour, particularly her nighttime encounters with a prostitute named Carol (Lily Frazer), Maud comes to believe that it is her duty to save Amanda's soul from damnation.
Saint Maud is the feature film debut from writer/director Rose Glass, who presents a psychological horror film about a hospice nurse, who is deeply religious for all the wrong reasons. Maud is a very lonely woman with a troubled past, who has seemingly turned to God because she has no one else. Believing her multiple seizures to be a sign from God, Maud begins a dangerous path of zealotry, as she becomes determined to save Amanda's soul, whether she wants help or not.
Save for a number of quick flashbacks and a couple of interactions with her old friend Joy (Lily Knight), Rose Glass makes the conscious decision in Saint Maud to keep the troubled backstory of its titular protagonist ambiguous. However, it does become obvious that Maud is suffering from some sort of mental illness, which leads to increasingly self-destructive behaviour. Structured as a drama for most of the running time, the horror of Saint Maud arrives at unexpected and very well-edited moments, including a very effective jump scare that arrives completely out of nowhere. Altogether, Saint Maud makes for a well-done character study that strikes an interesting parallel between religious zealotry and mental illness.