A quiet carer starts her new job looking after a faded, cancer riddled socialite. Maud (Morfydd Clark) begins in earnest after a very brief exchange (and an uncomplimentary comment about her new employer) with her predecessor.

Amanda Kohle (Jennifer Ehle) is dying of cancer and as Maud internally suggests to god he’s ‘likely to be seeing her soon’. Kohle, is a former dancer, who had and to certain extent still is a larger than life character, who drinks and smokes too much with a healthy sex life. She’s quite taken by Maud when her cross slips out and notes that she is a recent convert.

The two begin to get on, though its fragile, with Maud reminded of her recent past (that comes to face her when she bumps into ex colleague Joy (Lily Knight) and when she briefly goes off the rails) when Amanda gets drunk and with what Maud perceives as her promiscuity.

As the relationship develops so Maud’s mood changes, she becomes brighter, less uptight driven by the idea that she is doing god’s work and enlightening Kohle’s life. Her faith (or fantasy) is such that she has no inkling that she is being toyed with by Amanda. Maud pushes too far eventually resulting in an incident and her losing her job. It’s then back to her grotty room; alone with her beliefs and thoughts.

Reading through the credits it is remarkable that this incredibly powerful and assured film is the debut for so many people in different departments. It is of the highest quality with a perfect balance of effects, lighting, sound and music. Powered by a superb complex script Rose Glass and her sensitive direction. Yes sensitive, this is a horror film that looks at highly emotive and very difficult issues with some care, simultaneously developing a skin crawling tension that is truly unsettling for the viewer right up to the final frame.

The set designs, special effects and lighting are exquisite and hold up to repeat watches as previously occulted details and subtleties emerge. The sound design and sparse heavy pulsing score – by Adam Janota Bzowski - are of the first order getting under the flesh right to the bones, it’s a remarkable piece of work.

The central performances from Clark and Ehle are astonishing as their different philosophies on life emerge. Ehle’s is broader and one we are more familiar with but her own mortal fears mean she doesn’t descend to socialite stereotype. But it is through Clark that we see things, her matter of fact internal monologue, carefully layering her character. A complicated person (who as we pick up would not be totally unfamiliar with aspects of Kohle’s bohemian lifestyle) fighting to get back her life after an incident through her new faith, which she questions when things take a downturn.

Saint Maud is a staggering achievement that sets it up for film of the year and possibly one of the best of the last decade. Kudos too to the powers that be for holding out for a cinema release where it must be seen.

Saint Maud goes on general release in UK cinemas from 9 October.