The Dice House, Arts Theatre London

The title may suggest David Mamet, but Paul Lucas's play The Dice House (based on Luke Rhinehart's novel The Dice Man) owes more to Joe Orton, specifically What the Butler Saw (in which lunatic doctors run an asylum full of wrongly-incarcerated sane folk). Here Dr Ratnor (a hilariously imperturbable Neal Foster) presides over an isolated, decrepit nut-house - there may not be bats in the belfry but there is a bird nesting in the entrance hall. The radical psychiatrist makes all the residents, himself included, determine their actions by a roll of the dice - odds, two patients can have it off; evens, they'll have to wait. When a murder is discovered, the same procedure decides whether or not the police are called - morality and self-preservation alike bow to the workings of chance.

It may seem unfair to judge a young playwright's work against that of the master of Dionysian farce, but when someone helps himself so liberally to another's treasury he can't really protest an audit. The Dice House is often very funny indeed, from its opening scene in which the evil psychiatrist Dr Drabble muses on his wife's behaviour ("When she wanted me to sleep in the spare room, I put it down to the enigma of womanhood") and then tells a timid patient that, if he doesn't kidnap Mrs Drabble, he will be sectioned. "That is," the patient hesitantly replies, "in some ways, blackmail." We doubt the doctor's judgement when, on his producing a drug-filled eclair to aid the abduction, his accomplice asks: "Do I hit her with it?"

Orton, in his best plays, maintained a surface plausibility for which an underlying seriousness was essential. But too often in The Dice House Lucas loses control and his comedy starts less to resemble Orton than a heavy-handed Sixties spoof on free-love communes. Too much occurs that is silly without being funny; too often the writer or actors are overemphatic and smug - Jeremy Crutchley, in particular, dissipates his attractive stage presence in this way. (As his spouse, Lucy Scott, despite her enthusiastic conversion to all manner of perversions, maintains the cheerful refinement of the gentle, jam-making persona she had before being "liberated from the chains of ego".) Lucas also strays unwisely into fantasy and 10-ton irony with an assassin in a black diving suit who repeatedly menaces a paranoid patient desperate to believe his enemies are all in his mind.

The central premise, however, is attractive, and one almost believes Dr Ratnor's enthusiasm for dicing with life. The play is at its most appealing when it concurs with our guilty wish for a riot of id, and at times takes on some of the innocent glee of the pantomime. "We'll soon put a stop to that!" says Ratnor stoutly, but then remembers to throw the dice and adds, just as stoutly, "Oh no we won't!"

To 27 March (020-7836 3334)