Anthony Neilson is a remarkably prolific man, with a score of radio and stage plays to his 40-year-old credit. Some have titles like Penetrator, Twisted and Stitching, which may raise an eyebrow. Several have explored the male psyche but in this award-cluttered piece from the National Theatre of Scotland, which first took Edinburgh by storm in 2004 and is at the Playhouse all week with its original cast and direction (Neilson's own), his focus is on Lisa, a young mental patient (Christine Entwistle, excellent throughout).

I somehow doubt whether any of Proust's 12 volumes has appeared on Neilson's bedside table. Yet the play is in fact all À la Recherche du Temps Perdu. Lisa is luckier than the poor souls who thought they'd lost 11 days when the calendar changed. She's in quest of one hour lost in transit between time zones and delayed planes. That lost hour is rich in vital force. Lisa has become slow and alienated, while all its life and strength have gone to create Dissocia, a vivid world of magic, colour and random events.

Lisa's journey and adventures seeking her lost hour in Dissocia occupy the first act, in an amalgam of recollections of pantomime, surreal carnival and free-association Goonish word-play. There are In-security guards, time flies, small hours, an endearing Polar Bear and a lot of lost' things - lost inhibitions, lost arguments, lost sense of humour, and (sadly for Lisa) lost Lost Property. There's a flying car (Neilson loves Chitty Chitty Bang Bang) that turns into a bomber with a lot of noise from sound designer Nick Powell and magical changing light from lighting designer Chahine Yavroyan.

The final battle reveals the dreaded Black Dog, enemy of the realm of Dissocia, as Lisa's former boyfriend Vice. Their silent confrontation ends the act, but surely should have more substance. In the second act Lisa lies mute and motionless in the reductive normality of a psychiatric ward, visited by an interchangeable sequence of nurses bearing medication, doctors with clichés and clipboards, and a harshly uncomprehending sister, the outside world suggested only by the play of light on the glass-panelled door and the quiet ominous approaching footsteps. Finally, Vince offers, among useless gifts, a toy Polar Bear, which restores the warmth and glow of Dissocia.

We are to conclude (though Neilson doesn't quite say so) that surreal ecstasy and extreme experience are not only valuable but preferable. To my mind, the dubious shade of R.D.Laing hangs heavy over the work, and questions like these have anyway been aired more fully and much more subtly in Equus. However, the audience loved it, especially the four-letter words.