An interviewer should know something about his subject before he goes into the interview. It is, surely, a basic rule. Yet by the time I sit down with director Emma Stirling and lead actor Arthur Sturridge, I find I still know next to nothing about When The Rain Stops Falling, the recently written Australian play by Andrew Bovell that has the coveted honour of playing in the ADC mainshow slot this week. Since that slot is normally given over to the blockbusting likes of pantos, Shakespeares, and Broadway hits, I am curious to find so little about the play online. One review says that to describe the plot would be “murder”. It seems this portrait of a family, the Laws, spanning thousands of miles and a hundred years (some of them in a rain-drenched, globally warmed future) is a truly left-field choice.

So why this play? “Because it's beautiful.” says Stirling simply. First put on in 2009, at the Almeida in London, it has seen few revivals despite being what she calls a “modern classic”. “It deals with family and redemption and loss, universal themes.” It is a brave play in that it addresses the difficulties of functioning as a family in a confrontational way – shows us how characters in 1950s London hand down their problems to a 2039 Australian Outback, rather in the manner of the book (and forthcoming film) Cloud Atlas. Stirling sees its non-linear storytelling as showing a more real image of the drama than you could possibly get if it was confined to one room. “In a normal play, the themes of loss and the like seem clear cut, but in this play you can see the vast context they come in, and that muddies the waters. It puts the mundane in an epic frame.” Sturridge points out that the play is in a way about the end of the world, but this is only made heartbreaking because we can see the family involved, and how grounded they are in real, complex life.

Is it a tragedy, then? “Different people will feel different things” he says. Some people might see redemption in it. Fate is certainly at the heart of it, the way that past events determine how we live in the present, and we can see what is coming because of the order we see the play's events in. There is something biblical about it all, says Sturridge, how the sins of the father doom us. It is in many ways a very old play indeed. Sturridge's patriarch of the Law family compares himself to Saturn, who devours his own children, and the notion of a family carrying its curses through the ages is reminiscent of the Oresteia – Part II English students in search of what a modern tragedy might look like are advised to see this play.

Certainly the play is full of symbolism: a Biblical flood, nature being pushed to its limits alongside the humans it surrounds, a desert at the heart of Australia that seems both an “outside” and the place that truly links all the characters – it is a very finely constructed play in its metaphors. And it could only be done on stage: “There’s a very strong visual feeling of shared space”, says Sturridge. “You see one set of characters of one time zone finish their scenes as another set come on. History is repeating itself, and you feel it viscerally.”

Stirling explains how this works in her use of the ADC stage: an island with those shared rooms from different eras surrounded by a “memory space” where reality blurs as characters watch themselves as younger people. TV screens help to bring the non-chronological action to life – the characters can watch themselves and their recorded echoes literally in front of the audience. The tech “is going to be a nightmare” says Stirling ruefully, given all the evocative multimedia used – soundscapes, images and lighting becoming a total theatre experience. It’s not quite a fantasy, she says, but she’s certainly going to fudge where real life begins and ends. “It’s going to be beautiful”, she sums up with a secretive smile.

The actors have the unusual task of playing older and younger versions of the same people (one character is helpfully played by two actors both called Olivia). Stirling kept them apart for as long as possible, developing into individuals, before at the last moment introducing the two versions to each other. The results were extraordinary: mannerisms shared between the versions of a character appeared spontaneously as the actors intuitively co-ordinated the work they had done up to that point.

It is a play about the end of the world in many ways – Australia as the furthest point away from Britain, the last outpost of colonialism, and in the possibility of an ecological disaster, the very modern idea of apocalypse. Yet we don’t know how much of the apocalypse is real and how much of it is just a personal metaphor for these people, says Stirling. We never see the flood ourselves. “It stirs you up, this fantasy, because we understand it – what if it really did never stop raining?” says Sturridge. A play with this much ambiguity, this much trickery with time and place, makes it a puzzle that we the audience must unwrap – “it’s great as an audience member to actually have an active part in unpacking a play”, says Stirling. Combine some ancient and awe-inspiring themes with the twists and turns of the plot and the characters – how many plays do you see where you genuinely don’t know where it’s going when you begin? – and you have more than enough reason to go and see a play you never heard of before.

 When The Rain Stops Falling is playing at the ADC 23rd - 27th October, 7.45pm