If you want to see really interesting theatre for children, you should go and see work for the under-fives. No, let me put that another way. If you want to see really interesting theatre for anyone, go and see work for the under-fives.

There is a bit of a boom at the moment, perhaps because once companies are freed from the constraints of language as the dominant means of communication, they - and therefore their audiences - are also freed from the constraints of the "well-made play". As one practitioner put it at a recent conference, the under-fives are notoriously ignorant about the fourth wall.

The logical step is to make your theatre interactive, and that is just what Oily Cart have done with this 70-minute promenade show, set in a series of linked playhouses that constitute a giant maze. The child-sized houses have been constructed with the help of children during workshops in schools and have a wonderful fantasy element (like every picture of every house you've ever seen in a fairy tale).

But one of the playhouses - Bill's - is not finished, and the theatre manager is coming to take it away unless the audience can bring it to life. The children's task is to visit each of four playhouses, with the help of four musical builders called Dazzle, Sniff, Zoot and Fluff, and provide the smells, sounds, visuals and sensations needed to bring Bill's house alive.

One house is full of pot-pourri, velvety cushions and whiffs of fruit, soap and candy. In another, the walls are lined with CDs, and we learn a song in which the telephone goes "baa baa" and the baby goes "ding dong", while in a third house the children make fans out of streamers. In the final house - which is made from children's drawings - we make images of ourselves, which are projected on the wall.

Then it's back to Bill's house for the final transformation, as slowly but surely the house begins to come alive, with the clock ticking, the fire crackling in the grate and the baby wailing. It is about as magical a theatrical moment as you are ever likely to see.

The show, which is still in embryonic form, is a little rushed. Currently you are so busy getting from one house to the next that it is difficult to appreciate the journey, which takes you through a wide range of touchy-feely experiences. But this is a really wonderful idea, and I reckon as many adults as under-fives will be queuing to get in.

• Till Saturday (0171-265 9994). Touring to Luton, Cambridge and Windsor in the new year.