Director Gerard Johnson’s last feature was the impressively stacked Muscle, a dark thriller featuring a never-better Craig Fairbrass as a menacing personal trainer in Newcastle who takes over the life of his client Simon (Cavan Clerkin), luring him into a sinister subculture. Polly Maberly played Simon’s distant wife whose froideur partially sets the plot in motion. So while it’s easy to forget Maberly’s involvement in Muscle (honestly, the only thing I can remember about the film is Fairbrass and the orgy scene), she gets to take centre stage here in this similarly weird, skewwhiff thriller, this time set in London. And while Odyssey doesn’t coalesce as satisfyingly as Muscle did, that’s not Maberly’s fault. A character actor whose credits include a lot of schlock TV, she gets to be extraordinary here, playing a brittle, funny, completely deluded screw-up whose life comes unravelled.

Maberly plays Natasha Flynn, a small-time estate agent who runs an office with just two other employees, dweeby Spike (Charley Palmer Rothwell) and put-upon Safi (Kellie Shirley), plus new intern Dylan Rose (Jasmine Blackborow). Sometimes, Natasha sweet-talks her staff but more often than not she’s shouting at them, a capriciousness partly fuelled by her steadily increasing intake of cocaine. Completely fluent in the half-truth language of estate agentry, where small spaces are “cosy” and properties in the middle of nowhere are “rural”, Natasha worryingly believes her own lies, especially the one she tells herself about how the upcoming merger with another agency won’t be a takeover. In truth, the wheels are coming off her little toy wagon one by one; she owes money all over town, to old friends and loan sharks. She even owes money to the dentist’s surgery we see her skipping out of in the opening scene, without paying for a wisdom tooth removal.

The setup is promising and some viewers may feel as if they’re being primed to expect a comeuppance for Natasha, especially since estate agents may be the only type of professional less popular than dentists. But instead the film takes a weird zigzag into Grand Guignol horror territory, when Natasha is compelled to assist in the kidnapping of another estate agent called Douglas Kelly (Ben Shafik), at the behest of a third, Dom (Daniel De Bourg), and keep Douglas tied up in a lonely property in Essex called Calypso Farm.

That Homeric echo in the name of the farm may get you thinking that this is gearing up to be a sort of pastiche of the Odyssey – but no, there’s no going home for Natasha, only forward and deeper into a kind of demented madness. The bloody excess of the last act doesn’t feel earned or even very logical, but Maberly is so watchable and intense you can forgive the film its sins. It helps that Johnson gets such a substantial assist from the soundtrack, created by his brother Matt Johnson, best known for his band the The, who produces a pulsing, menacing electro-forward score.