Here's a dilemma for a 13-year-old. If his heart is pure, he'll be granted three wishes, but if his heart is not pure, he'll be turned into a goblin the size of a thumbnail.
Will Tuckett's new family show in the Royal Opera House's second theatre contains many such colourful curiosities. It's based on a story from 1001 Arabian Nights – the one that became a moustache-twirling Douglas Fairbanks film in the 1920s, and an over-perfumed remake in the 1940s. What gives Tuckett's version youth appeal, now that the notion of Baghdad as a city of dreams is no longer viable, is that he ingeniously runs two stories at once.
The first supplies the realist strand. Three children have been separated from their families in the fallout from an unspecified war, and take refuge in a cave. At least it looks like a cave, until we and they realise it's a bombed-out theatre, complete with crates of props, costumes and even a stage door man, who suggests that, to take their minds off cold and hunger, the children might act out a story. The elder girl leaps at the chance of playing a princess – though throws a strop when she learns about enforced marriage. The younger wants to be her pet monkey. The boy, typically, won't join in, but eventually agrees if he's allowed to play a petty criminal.
Thus Tuckett ropes in even the most recalcitrant spectator, and the Arabian Nights story unfolds remarkably intact, complete with scenes in Persian palaces, dungeons and market places, involving genies, a levitating carpet and the statutory heap of jewels promising wealth "enough to buy the world", but which, on being touched, unleashes a storm of terrifying black-clad, baton-wielding troops. There's symbolism here to keep an older child asking questions till next Christmas.
Jon Bausor's designs, Colin Grenfell's lighting and Mervyn Millar's puppetry pull wonderfully together. The ballet of flying fish is a luminous marvel, the winged horse so beautiful you hold your breath. Who could guess that, when a dust-covered paratrooper stumbles into the cave, his backpack will unfold into a silvery equine neck and head, creating an entire animal capable of stooping to drink, or nuzzle a man's hand?
The original music, by Paul Englishby, for five-piece band, explores a range of vigorous Eastern styles, but gains authentic bite from improvisation. I loved the way the Turkish duduk was used to underpin the genie's speaking voice, giving it a swooping, supernatural fuzz at the edges.
Frankly, this show would work without its dance element, but what there is is apt and good, and threads naturally through the action, without pulling the narrative up short. Performances are strong: Valentina Golfieri's monkey scamperings are highly entertaining, Charlotte Broom as the "princess" is appealingly un-girly, and Christopher Marney's "thief" reveals his transformation to "prince" in the subtlest ways.
Tuckett's shows are going from strength from strength. Soon he'll need a bigger theatre.
To 3 Jan (020-7304 4000)