The Nest, Traverse Theatre, Edinburgh

If there were a competition among playwrights to create the most isolated, barren location in which to dump one's characters, Alan Wilkins's storm-bound bothy deep in the heart of the Highlands, with no running water, no furniture and no way in or out except through the trap door in the middle of the floor, could beat off the competition with the flick of a Gore-Tex-covered finger.

In this dark walkers' hut recreated downstairs in the aptly stifling atmosphere of Traverse 2, the hatch in the steeply sloped floor is a wonderful device, not only ensuring a sense of claustrophobia but also making every entrance and exit in this often witty first play a brilliantly laborious affair.

First through the hatch is Helen (Candida Benson), desperately and bitterly maintaining an iced-over heart beneath her shivering exterior toward her cheating husband, Colin (Matthew Pidgeon). Her carefully nursed, vengeful obsession is reflected in their five-year attempt to climb all the Munros (mountains in Scotland higher than 3,000ft). There is a rather overdrawn tension to these first few minutes, amplified as the two are joined by "Honest" Mac (Lewis Howden), a bodyguard on a continuous walk of the Munros (all 284 of them), who has just plucked a countryside-virgin photographer, Jackie (Clare Yuille), from certain death out on the hillside. Wilkins racks up some suspense with a fifth rucksack, whose contents are disgorged with all the gleeful makings of a horror movie.

But for all the Munro-talk of how many and how often, and for all the implications of the closed-in bothy, Wilkins is here concerned with a wider scope of human relationships - the ones you carry about with you, the ones that died long ago but still maintain an outward semblance of unity, and the flicker of the new, with all its potential for conflict subtly drawn under a gloss of humour. Wilkins has a great feel for one-liners, and there are fine touches in Lorne Campbell's assured direction. But despite original moments and rigorous characterisation, Wilkins's ambitious, tightly drawn play fails to convince a little too often on the basic level of human interaction.

It's partly to do with some loose plotlines - the ostensibly storm-bound inhabitants of the bothy look rather ridiculous as they talk of the awfulness of being stuck in the bothy when one of them pops down the shops. Wilkins seems to ignore the human veneer of politesse between strangers, which one feels would undoubtedly, at least at first, reign in this enclosed space, and his characters launch immediately into subsequently unconvincing judgemental attacks on one another.

It's unfortunate, because he has created a fascinating character in Helen, and some great set pieces. Whereas Colin's adultery is rewarded with a series of romantic, emotive speeches in which he has achieved contrition, Helen, who dares to try to make him feel her hurt, is vilified.

Tempting though it must have been, Benson doesn't try to make her character sympathetic. She plays Helen as an abrasive moralist, but skilfully gives us the occasional glimpse of a kinder-hearted, tender soul beneath - and of a play with more layers.

To 2 May (0131-228 1404)