When little Billy is invited to step inside Mr Magico's mysterious cabinet, it is as if all his birthdays have come at once. Or all his next 25 birthdays, to be precise, as he steps out again the same age as his dad.
This is as much a surprise to the Great Magico as it is to Billy's horrified mother, who storms into the cabinet to retrieve the missing seven-year-old - only to re-emerge seconds later on the wrong side of puberty. At this point the madness stops - or, depending on how you look at it, begins - as sensible Polly decides to stay right where she is inside her 11-year-old body, in order to figure out a way of restoring her family to their respective generations.
Christmas time in Scarborough usually offers Alan Ayckbourn an opportunity to indulge in one of his elaborate games of time travel. But whereas recent children's shows, such as the sublime Whenever, have adopted a fantasy layer of fairy-tale Victoriana, The Jollies is set resolutely in the here and now.
Polly's problems are modern problems. Having to explain the situation to the social services, for example. Or trying to work out how to make a living when the breadwinner is aged seven, and your mum is nine years short of being able to resume her job in a betting shop.
I do not know how the Stephen Joseph Theatre's casting department got their heads around this one. But the show features outstanding performances from two terrific, tiny actresses, Charlie Hayes and Jo Theaker, whose diminutive stature belies their sizable talent. Robert Wilfort and Becky Hindley are also great as the larger versions.
It increasingly becomes clear that Ayckbourn's work for children is not an alternative strand to his adult plays, but a direct continuation of them. His recently completed trilogy, Damsels in Distress, plays with the same theme of young women thrust into adult situations, and Polly's resourcefulness makes her a sister to them.
The Jollies is like a cheerful scherzo to the symphonic complexity of the other three plays, and will certainly thrill the kids this Christmas. But it is really a grown-up play trapped inside a child's body.
· Until January 4. Box office: 01723 370541
