Oxford theatre has wandered into science fiction. Into a place where aliens eat pickled eggs and families crawl into their basements to survive the apocalypse that’s coming. Or rather, it has wandered into the minds of the kind of people that believe in aliens and apocalypses, telling their stories, and unpicking their lives.

Wax House Theatre’s Doom’s Day, this year’s OUDS National Tour, tells the story of doomsday prepper Joseph Doom, in his own words – much of the script is lifted from one of his many free e-books about his life. The cast multi-role their way through the story, swapping checked lumberjack shirts and American accents – some good, some less good – to depict ‘a child of the 60s’ who became increasingly disenchanted with 1970s America. Director Laura Day is impressively experimental in the range of theatrical techniques they have built the production upon, packing it full of soundscapes, movement sequences and lip sync. Matilda Hadcock was particularly good at embodying the voice of a Sarah Koenig-esque reporter, all crisp gestures and curiosity. And James Walsh, for me the stand out actor, did a lovely job recreating the moon landings with nothing but tin foil and breath control. But at times, it feels like the production is rushing through a theatrical chocolate box of styles and techniques, for a purpose we never quite discover.

By the end of the show, we really do know a huge amount about Joseph Doom – what his schooldays were like, where his family comes from, his strange and faintly disturbing romance with his school-teacher-and-then-wife. Why? His was a moving story, especially in the moment he must painstakingly undress his wife after she has suffered a stroke (a moment they could even have made more of). But is it an important one? I don’t think this production quite knew.

A production that does know exactly what its point is Poltergeist Theatre’s (one of New Diorama’s Graduate Emerging Companies) Lights Over Tesco Car Park. The four principal characters, gradually established as a group of Oxford students who befriend a shadowy figure called Robert – a man “in communication” with an extra-terrestrial – strike an immediately comfortable rapport with the audience. They share our sceptical view of Robert’s sightings, inviting us to laugh at the titles of internet articles like ‘The Same Aliens That Killed JFK Just Rigged The World Cup’, but also constantly push us to pick over our assumptions about what makes something true. ‘If I told you that the brownie I gave you earlier was made from my poo, does that make it less delicious when you ate it?’ asks the slightly whacky Julia (Julia Pilkington), while the other characters cringe along with the audience.

But director Jack Bradfield has made sure that the show is never really embarrassed by its own weirdness. Confidently, deftly, the cast invite audience members onstage to join them in recreating various real life UFO sightings, with some wittily imaginative assistance from water guns, balloons and flying saucers. And by the end, you realise that the work of the play has been to gently widen its interest in UFOs into a much bigger, and more theatrically pertinent, question about belief – because, in the theatre, we choose suspend our disbelief all the time. Plunged into the dark in the final scene, the four actors lift up their phones, fingers pressed over the torch light to make four dull red pin pricks. I know it’s an iPhone, but I’m seeing an alien. It’s a choice I make, that all the audience make, and truth has very little to do with it. We share a moment, witness an illusion. That’s the power of theatre, and that’s why Lights Over Tesco Car Park is more than just a play about aliens with a delicious Bowie soundtrack.

This article was corrected 18/08/18 to reflect the fact that Laura Day was the sole director of Doom’s Day.