People who know Romola Garai from her appearances in period dramas such as Atonement and The Hour (and fundamentally misunderstand the concept of acting) will be shocked by her directorial debut: a grisly horror movie about a traumatised ex-soldier (Alec Secareanu) in a demonically possessed house.

Amulet swings pendulum-like between Tomaz’s past in an unspecified warzone and present-day life in London, where he lives with a woman called Magda (Carla Juri) who cares for her dying, attic-dwelling mother (Anah Ruddin). It begins in the realm of British realism before twisting into something feminine and cosmic, almost a cross between Ben Wheatley and Julia Ducournau. Unlike Titane the film does not necessarily hook you immediately but rewards patient viewing, like crawling through an evil tunnel towards some distant, radiant light source.

Indie contemporaries Relic and Saint Maud hang in the fetid air of the crumbling house, all mouldy crevasses and bats in the toilet; “They are born with teeth,” says Magda, probably more a comment on original sin than a statement of biology. Tomaz sees her as an object of salvation, but Garai has other ideas. Her horror is indirect and writhing, subverting genre clichés of nans and nuns (a wicked Imelda Staunton) to deliver a disturbing treatise on greed, cowardice and male violence that combines The Brood‘s female viscera with Martyrs‘ cleansing punishment.

Murky and meaty in more ways than one, Amulet may be tough to get into but it gnaws and shreds away at your nerves. This is a bold calling card for a director who proves extremely resourceful, and less interested in filling seats as soaking them.