THE game's afoot and there are games to be played by the audience in Alexander Wright's contemporary, interactive original drama inspired by Sir Arthur Conan Doyle's detective stories.

From his Belt Up Theatre beginnings to The Flanagan Collective's pub-theatre take on A Christmas Carol, Wright has married smart script-writing with moral fibre, mischievous humour and a love of family parlour games from the days before computer games.

The English are considered to be a reserved race, but Wright gleefully flouts such conventions, encouraging everyone to throw caution to the wind through a combination of advance warnings in each show's literature and then the skills of the cast members at cajoling participation. How apt that Holmes, Watson and audience alike should end up wearing party hats.

This Sherlock Holmes show is not so much elementary as complementary and supplementary, such is the relationship between cast and viewers, whose involvement in A Working Hypothesis begins in the pre-show chatter over drinks. Sticky name tags are issued to assorted audience members, ready fodder to be picked out and worked over by the eminent German Selohm Socklehr (Dominic Allen), honorary professor of Criminology at the new University of York.

Yes, you read that correctly. Wright has set his play amid the Cold War tensions of 1963, the university's opening year. It does not take great powers of anagrammatic deduction to work out that the man giving his inaugural lecture on Sherlock Holmes and his Science of Deduction and Analysis is in fact Sherlock Holmes, three years after his presumed death at the Reichenbach Falls.

Enter Dr Watson (George Williams), not best pleased at his best friend's silence in the intervening years. Cover blown, Holmes reveals his real reason for giving the lecture: to entice Professor James Moriarty out of the woodwork, in this case the woodwork of the York Guildhall Council Chamber. It is a compact, combative amphitheatre, claustrophobic too, a place of natural tension and decision-making, suited to theatre with a "trapped" audience in direct contact with the performers.

Tom Bellerby's production cracks on apace, even keeping the audience busy at half time, when divided into teams to work out clues from books and information on the walls to assist Holmes, squeaky pen ever at the ready for his overhead projector.

Working in tandem with their audience link Lucy Farrett, Allen and Williams are experienced hands at interactive theatre, while Allen's ever quick wit enables him to improvise. He may not look like a conventional Holmes, but he shares his unpredictable nature and fierce intelligence, while Williams has the honourable, everyman quality that Wright sees as so important in Watson when faced with the erratic "Superholmes": the everyman hero holding the superhero's excesses in check.

Wright's play is a combination of the playful, the practical, the pugilistic and the problem-solving, with a storyline that finds room for pranks, sword-fighting, firearms, physical theatre and sly intelligence...and Moriarty? Play the game and you will love it; be stuffy and stand-offish and you won't.

Sherlock Holmes: A Working Hypothesis, The Flanagan Collective, York Guildhall Council Chamber, until September 21. Box office: 01904 623568 or yorktheatreroyalco.uk