After is very much a theatrical experiment, with not one but two unusual cards to play. First of all, the 20-minute script is performed twice, once with two female actors and then with two male ones. And secondly, each of the pairings is made up of a real-world family – one a mother and daughter, the other a father and son.

Each spin through sees the parent and child scavenging for food in a sparse, post-apocalyptic world. (The exact nature of the apocalypse is one of the script's secrets. I can reassure you, though, that there aren't any zombies.) This is a day, we sense, that's been lived through many times: the same tasks, the same stories, the same quarrels. But today, all these tensions will finally come to the boil.

Playwright Craig Jordan-Baker packs a lot of ideas into such a short script. Most intriguing, to me at least, is the process of society becoming feral: not a collapse of civilisation, but the gradual loss of it. Mum or dad represents "the Before", the time we know, while the child embodies the future – a generation that won't remember or even care about the things that have been lost. Even language itself, it's suggested, is destined to fizzle and die.

These are all interesting thoughts, and there's a big surprise at the end of the piece to shake up your perception of what you've seen. But what's fascinating about After is the character-building – and specifically, how two directors can find unrecognisably different personalities within the same text. In the first, female piece, the mother is tough and practical: willing to do whatever it takes to keep her daughter and herself alive. The male version, in contrast, responds to the script's use of complex words and language, painting the dad as a slightly professorial figure who's nonetheless adapted to a new reality.

The children's roles are equally diverse. Echo Phillips gives us someone we know from our own experience, epitomising youthful rebellion against parents and the remnants of society; while Dan Dussek emphasises a return to nature, using all four limbs to spring across the stage with impressive physicality. The seeds of destruction are a little different too; Syreeta Kumar as the mother suffers the fate of a deposed leader, while Tom Dussek as the dad is overtaken by his own restless mind.

And of course, by the time you see the second of the two versions, you know the twist in the tale. Did that add an extra piquancy to the portrayal – or did it lose something by sacrificing the element of surprise? Even after seeing both pieces, I don't know the answers to those questions… but I had a lot of fun speculating all the same.

So, four stars if you'll enjoy that kind of debate; if you just want to watch a straightforward piece of theatre, call it three-and-a-half. Either way, After is a rewarding experiment, and a fine showcase for the talents particularly of the two young performers. Great things lie ahead for them, I'm sure.

We reviewed After at the Rialto Theatre. The run there has ended, but there is an additional date at Brighton Spiegeltent on 28 May.