Kicking A Dead Horse, Almeida Theatre, London

Is he alone and unobserved? You bet. Hobart Struther is in the American desert, digging a grave for the title animal, with only the wind and rocks for company. Yet, despite his need to conserve water and energy, Hobart not only digs a huge hole but spends 80 minutes loudly reminiscing, worrying, raging, and regretting. Since he was created by Sam Shepard (who also directed) and is embodied by Stephen Rea (for whom the play was written), Hobart has a fair-sized claim on our attention. But it does not take long before we realise that he could have been originated by any number of angry old men, lamenting their lost youth and strength as well as America's and conflating the two.

Hobart's labour is intensified by the literary burden he bears. His loneliness, his clowning, and his hole evoke Beckett, but the Irish playwright's influence is at least equalled by those of American novelists. While his name evokes Lambert Strether, the unworldly middle-aged man sent east by Henry James to grow up in The Ambassadors, Hobart's situation – the result of a quest for "authenticity" – brings to mind that of numberless fictional Americans whose search for truth is stopped by a bullet or worse.

Hobart has fled New York, leaving behind a wife who was once "beyond authentic", but with whom he has long since settled into a routine. The self-hatred of this former cowhand has become so intense that he has been throwing "masterful" million-dollar paintings out of the window on to Park Avenue. So Hobart returns to the West, where he began his career in art by cozening yokels out of unregarded treasures, and broods on his and America's crimes.

Banal and inflated though this is, Rea attacks it with soul and skill. His voice, dry and pinched, cautiously plays out the reins of his desperation, then harshly yanks them back. But he is forever battling against the perfunctory and self-pitying quality of the material. Though some may interpret the final catastrophe as a demonstration that even good, idealistic Americans are doomed, Hobart's fate suggests more strongly an extreme expression of the desire to retreat, sulking, and pretend that one has died, or the world has. The last action of Shepard's play may create an almighty bang, but emotionally and philosophically his play ends with a whimper.

To 20 September (020-7359 4404)