Scattering Salt is the story of two lovers, affectionately known to each other as Horse and Cart. Horse is here, with us in the room, an abandoned tiled chamber below Brighton Town Hall; Cart is somewhere else. But her essence is present, captured on video… and she’s reaching out to us through a mirror, which walks and talks and is played by a woman in a reflective dress.

The set-up’s bizarre and quirky, but it isn’t surreal. There are rules to the parallel universe we’ve been transported to, and challenging ideas in play - all of which, over time, we come slowly to understand. There’s a very serious real-world story underpinning it all, and some of the thoughts we hear are unconventional to the point of being disturbing. But the treatment of them is always respectful - and whether you embrace or recoil from what Cart says, she’s sure to make you think.

There are upbeat, playful elements as well: most obviously the chorus of three “mermaids”, who appear at intervals to enliven proceedings with some backchat and a smattering of dance. Playwright Kit Danowski appears on stage too, in the persona of a fussy creator who can’t bear to let go. As a meta-theatrical gimmick that’s dangerously close to its sell-by date, but Danowski carries it off so wittily and lovably that it stops being a gimmick at all.

Matching the run-down space it’s performed in, the production feels purposefully rough-and-ready, but in truth there’s nothing ramshackle about the performance we see. Every now and then, video projections fill the wall above us, flooding the spartan space with movement and colour. The cast command the room too: Angela El-Zeind forms a warm if edgy connection in the first few minutes, while Ayse Evans is believable - sometimes distressingly believable - as the troubled Cart.

But I must warn you, dear reader, of the play’s one great downside… which is that it’s performed in the very tiniest of rooms, and most of the audience have to sit on the floor. Yes, the intimacy adds to the experience, and yes, the venue is a stunningly atmospheric one, but as we climbed the stairs back to daylight the chatter around me was all about how uncomfortable everyone had been. It’s a real shame, because this is a show that deserves to be studied and appreciated to the full - and I confess, there were moments when my tortured muscles screamed so loudly that I simply couldn’t listen to anything else at all.

But if you’re better at sitting cross-legged than I am - or if you have a mobility issue, in which case you’ll get a chair - Scattering Salt might be truly magical. Near the very end, as the threads all come together, we’re invited to take part in a simple but symbolic ritual before we pass back to the real world. I was ready for the ritual, and for what it represents; but as the script points out, there were times in my life when I’d have resisted it. That profound realisation is the show’s gift to me, and it’s all the more effective because it’s offered with so much charm and humour.