Mercury Fur, Menier Chocolate Factory, London

Just before the start of this strikingly designed traverse staging of Philip Ridley's egregious new play, a functionary comes on and points out the particular exit that can be used by members of the public if they want to leave prematurely during the interval-less two-hour piece.

Just before the start of this strikingly designed traverse staging of Philip Ridley's egregious new play, a functionary comes on and points out the particular exit that can be used by members of the public if they want to leave prematurely during the interval-less two-hour piece. He also announces that there will be no readmittance.

As it turns out, Mercury Fur is the kind of play that will make some people want to make an early bolt for the outside world, and one of the twists is that those so minded have to depart by trekking across Laura Hopkins's powerful evocation of an abandoned flat on a derelict east London estate.

The night I attended, there were about half a dozen deserters. It was fascinating that they all left individually; that they did so at widely spaced intervals; and that (above all) they did not seem to be leaving in disgust at an often blackly hilarious and deserving piece. Rather, one feels that the unremitting subject matter - summed up in the epigraph by David Leavitt: "Sometimes brutality is the only antidote to sorrow'' - became too much for them, regardless of Ridley's particular treatment of it.

Acted with a thrilling comic, wired-up precision by John Tiffany's superb cast, the play immerses us in a ravaged, dystopian London that seems to have been reduced to lawlessness by an invasion of hallucinogenic butterflies dropped by some unspecified enemy power. People who remember what life was like before are becoming few and far between.

Elliot (played with the serrated sensitivity of an army knife by Ben Whishaw) and his brother (Robert Boulter) are rushing to get the ruined apartment ready for a party for a kinky paying client - the pièce de résistance is not a cake but a specially reared prepubescent boy who isn't likely to leave that flat except in bits and in bags. And not of the "doggy'' variety, either.

Some may object that this figure, heartlessly named "Party Piece'', is brought on stage. Certainly, I can't imagine how the young actors who play him could come through the rehearsal process entirely unscathed. That important matter aside, it seemed to me that the play has the right to risk toying with being offensive to bring home just how morally unsettling this depraved, perverted-kicks world has become. If you could sit through it unaffronted on the artistic level, it would surely have failed in its mission.

The performances have an almost hallucinatory edge, while never becoming caricatures. Eyes groping helplessly around as she struggles to fix on to the next self-protective fantasy, Sophie Stanton is hysterically funny and unnerving as a tiara-ed creature nicknamed the Duchess, who is so off her trolley that she has muddled her own life story with the plot of The Sound of Music. A flawed evening (the political context is too conveniently hazy) but, I suspect, an indelible one.

To 27 March (020-7907 7060)