You’ve got to admire wife and husband film-makers Tori and Matthew Butler-Hart. Stuck in their London flat at the start of the pandemic, the pair wrote a sci-fi script together: a Groundhog-Day-meets-The-Matrix tale of a woman trapped in a time loop. They shot it à deux on an iPhone; she stars, he directs. And there are a couple of cameos, from Ian McKellen and Game of Thrones actor Conleth Hill (who quite literally phoned in their performances from home). It’s a genuinely impressive achievement, but for a film about the infinite possibilities of parallel universes, it’s exasperatingly samey.

Tori Butler-Hart is Jane, a woman who wakes up every morning tied to a chair in the attic of a London semi with no memory of how she got there. Outside, the streets are eerily quiet. Scared but resourceful, Jane finds a door hidden behind a pile of junk. A camera on the wall is watching – and from time to time the soundtrack picks up the voices of her observers, distorted and crackling.

Jane’s lockdown ordeal is replayed over and over again with slightly different variations – in way that begins to feel more ad nauseam than infinitum. Every day she wakes up in the chair, and every day gets a little closer to freedom: down the stairs, out of the back door, into a car. Then something happens to terrify her and bang, it’s back in the chair.

Appearances from McKellen (sporting a dapper lockdown beard) and Hill don’t add much. The pair play physicists from the Wytness Quantum Research Centre – the place Jane is trying to reach. They speak to camera, talking heads on a documentary, but, frustratingly, explain very little. What ideas are here never really come to life. Though perhaps in the future, the film will come to look like a lockdown time-capsule: a reminder of the fear and isolation of spring 2020, and the unnerving feeling of standing in empty streets in towns and cities as if the world has stopped.

• Infinitum: Subject Unknown is out now on digital formats.