The 1998 Guardian International Theatre award was scooped by writer/director Dylan Ritson and he proves that the faith was justified with this most novel of London debuts.

Ritson's play and production, a fleshing out of Lewis Carroll's nonsense poem, are overlong and the relentless wordplay can get wearing. But there is real imagination at work here, and the eerie, derelict upper floors of the museum are cunningly used for this promenade.

Having assembled his strange and unreliable crew of a ballerina, a baker, a banker, a barrister, a beaver and others, the Bellman takes us on an epic journey in search of the Snark. In Ritson's hands the mock-heroic nonsense poem becomes an eccentric marvel in which the visual conceits match the absurdity of both his and Carroll's language. The cleverness of the production is the way it gradually seduces you with the logic of its madness so the audience becomes almost as one with the protagonists as we are led deeper and deeper into the heart of the building. Eventually we are all quite lost too in the tangle of trees and Ruth Barrett's beautiful, itchy score.

Ritson holds back on offering some emotional payoff just a little too long, but the final half hour - a cross between the final damned days of Scott's doomed South Pole trek and Fitzcarraldo - has all the sense of loss and hallucinatory strangeness of a nightmare.

When Carroll was asked whether the poem was an allegory, a political satire, or contained a hidden moral he answered, "I don't know". But Ritson knows very well that it is about the foolishness of human desires, how we chase dreams and the way all our lives are a fantastical quest.

• To April 29. Box office: 0171- 960 4242.