Andy Arnold established his reputation at The Arches through evocative, site-responsive productions of Samuel Beckett's absurdist scripts; Karen Dunbar is best-known for her characters in Chewin' The Fat. Arnold's decision to cast Dunbar as Win, the protagonist of Happy Days, seems brave: Beckett's vision of a post-nuclear wasteland is hardly a vaudeville comedy.

Yet Dunbar's performance is stunning. Encased in a tower of sand – with only her expressive face and voice to expose the despair and longing hidden within Beckett's taut, precise language – Dunbar's Win is a monument to despair. Happy Days has little in the way of plot – a woman is buried in sand and submits to the onslaught of heat and misery – but Dunbar takes Beckett's script and exposes its brutal subtext.

Beckett's familiar preoccupations – the inevitably of decay, the horror of consciousness, the hostility of the universe – are rendered almost poetic, as Dunbar's Scottish accent ranges from lyrical to hysterical, her mobile features adding the devil to the detail. While Beckett's apparently abstract scenarios are often taken to be philosophical meditations on existence, Arnold's direction and Dunbar's performance reveal the human suffering beneath the soliloquies and the compassion behind the horror.