The Fahrenheit Twins, Pit, Barbican, London

I was once in Los Angeles in mid-December, reporting (for this paper) on Andrew Lloyd Webber's very imaginatively revamped version of Sunset Boulevard starring Glenn Close. The surprising thing about LA at such a season is the contrast between the mellow clemency of the climate and the fact that the vast majority of the private homes in their own large grounds are covered with artificial "Holiday Season" snow like some transatlantic Narnia in which Aslan has been toppled as deity by Perry Como.

All of this came back to me while I was watching The Fahrenheit Twins, the delightfully inventive, funny-sad new double-hander from Told by an Idiot. The set here – which consists of a miniature ski-slide (on which a little table is frozen in mid-slalom) and dinky living quarters with flaps for ice-holes and cupboards etc – is covered in just such a vision of fluffy ersatz whiteness. And the artificiality has a genuine tragicomic point to make in a show which, though it may be set in the real Antarctic and be based on a true story, focuses on a pair of identical twins who have been trapped in an artificial predicament by far from natural parenting.

The siblings are beautifully portrayed by Hayley Carmichael – who in demeanour, voice and temperament seems to me to be the Judi Dench of devised physical theatre – and lovely, generous, mock-amateurish Paul Hunter. The irony which runs through the piece is that the pair have anthropologist parents who are so busy monitoring the local tribe that they can't see that their own progeny are having to concoct complicated survival rituals every bit as interesting. Exiled into a kind of desperate, permanent innocence, the pair decide that they will be able to ward off change if they annually manage to blind a white fox before it has had a chance to see the snow.

The piece is enhanced by a music track that ranges from the congruent (a heart-stopping rendition of Catalani's aria "Ebben? Ne Andro Lontana") to an introductory blast of "Young Americans" that hangs round in the mind as a perpetual puzzle. Will the pair be better adults for suffering in such parky conditions? The answer remains forever a matter of speculation – the future congealed as a moot point at the end like the chair frozen in mid down-ward tumble at the start of this richly rewarding piece.

To 5 December (020 7638 8891)