One Flew Over The Cuckoo's Nest, Assembly Rooms, Edinburgh

Seldom can a show have attracted so much hype or so many column inches before inviting in the press than One Flew Over the Cuckoo's Nest . With a handful of the stand-up comedians who scored such success with Twelve Angry Men in last year's Edinburgh Fringe, director Guy Masterson embarked on Dale Wasserman's 60s classic drama. He soon withdrew, and when illness struck it seemed the show might be jinxed.

Seldom can a show have attracted so much hype or so many column inches before inviting in the press than One Flew Over the Cuckoo's Nest . With a handful of the stand-up comedians who scored such success with Twelve Angry Men in last year's Edinburgh Fringe, director Guy Masterson embarked on Dale Wasserman's 60s classic drama. He soon withdrew, and when illness struck it seemed the show might be jinxed.

But it's up and running and, with Christian Slater following in the footsteps of another notorious Hollywood hellraiser, Jack Nicholson, the part of psychotic drifter Randall P McMurphy has an effective combination of insouciance and manic energy.

The matronly "Rat-shit" - as McMurphy playfully addresses the all-powerful Big Nurse Ratched, accustomed to calling the shots - has met her match and the cowed "acutes" and bullied "chronics" have found a staunch ally. Frances Barber is certainly no "angel of mercy", her face as starched as her uniform, her smile emerges like a red gash across an expressionless mask.

When the mask starts to slip, the temperature starts to rise in Terry Johnson and Tamara Harvey's production. Barber has a compelling stage presence, disturbing in her seamless switch between nice and nasty as she goads and provokes McMurphy into the violence that will be his nemesis.

As McMurphy helps his fellow inmates in this isolated "therapeutic community" to find their collective voice, Brendan Dempsey's haunted Chief Bromden comes compellingly to life. His vivid imagination is brilliantly illustrated in his reminiscences, colourfully evoked against a background of airy panpipes, seductive birdcalls, and, for leaping salmon, swirling lighting.

Though the focus of attention as the irrepressible, rebellious McMurphy, Slater supplies plenty of opportunities for the rest of cast to respond sympathetically and characterfully with all the quirks and eccentricities they can muster. Mackenzie Crook is unaffectedly touching as the stammering virgin Billy Bibbitt, finally discovering that there's more to life than his mother and his medication, helped by the uninhibited Candy (Lizzie Roper). But it's hard to sense the gamut of emotions the text runs through and it all feels slightly superficial, more like a playschool in its comic plausibility than a psychiatric ward.

There's no strong sense that men have been trapped in time and place, physically and mentally cramped, all too readily acquiescing to a petty authority and ward policy. Perhaps, through making some cuts, an element of vital tension has been lost with the result that, as we spiral towards the tragic and optimistic conclusion of what should be a tougher and more substantial story, we're observing rather than involved. And when the emancipation from the straitjacketed confines of the restrictive regime finally occurs, instead of being exhilarating, Bromden's show of strength with the fuse control box is about as effective as a damp squib.

To 30 August, 1.45pm Returns only, 0131 226 2428. Then at the Gielgud Theatre London, W1; 0870 890 1105