How's your father?

I've heard of keeping it in the family, but this is ridiculous. Having just played Jocasta, mum and wife to Oedipus, that terrific actress, Lorraine Ashbourne, heads straight into the role of May, the woman who has much more than a blood bond with her half-brother in Sam Shepard's Fool for Love. It's only a matter of time before Ms Ashbourne makes her operatic debut as Sieglinde.

In Ian Brown's revival at the Donmar Warehouse, the actress is partnered by Barry Lynch, who plays rodeo rider Eddie, the sibling who has tracked her down to a godforsaken motel room on the edge of the Mojave Desert and is doomed to go on loving her and leaving her for ever. These are two of my favourite performers and they pull off certain riffs of extraordinary intensity here. But, as with all the English productions I've ever seen of this author's work, I kept getting the uncomfortable sense that what I was witnessing was actually a talented team on Whose Line Is It Anyway? who'd been told to improvise a Sam Shepard play. American actors have equivalent difficulties with the pauses and elaborately veiled power games of Harold Pinter.

Before Fool for Love, a Shepard play in which the woman gets as good a dramatic deal as the man seemed about as likely a proposition as a refuge for battered wives run by Ernest Hemingway. In Brown's production, though, the balance arguably swings too much in May's favour. The look-at-me, insecure swagger of Lynch's macho preenings - all that show-off lassooing of the bed knobs and the ludicrously phallic cleaning of his shotgun - is exquisitely funny and pathetic. But, to my mind, it showed us this character from May's point of view and not enough from his own. Lynch is better at projecting the calm, dangerous insolence with which Eddie runs laconic, self-amused rings round the ill-at-ease, slow-witted hunk (very well played by Martin Marquez) who comes to call on May and gets treated to the dreadful story of how their incest arose and the resulting suicide of Eddie's mother.

The drama takes place under the monitoring eye of the Old Man (Gawn Grainger) who fathered them - an irresponsible phantom who interrupts the action with his special pleadings and his shifty, highly American championing of fantasy over fact. Brown's production is at its most powerful when this figure forsakes his lofty chair and enters the motel room, creating a wonderful circuit of quiet disturbing energy as he gazes at his daughter gazing at her brother / lover. At first invading the space with a misplaced proprietorial confidence (adopting a position on the bed that brazenly mirrors the one his son took up), the Old Man is eventually reduced to a coward's unlovely wriggling as he tries to evade facing up to the terrible consequences of his stubborn, deluded individualism. Less than utterly convincing in her wall-banging paroxysms of demented frustration earlier in the play, Ashbourne beautifully transmits the drained stoical realism of May at the end. The spectre of Whose Line Is It Anyway? vanishes completely.

To 30 Nov. Donmar Warehouse, London WC2 (0171-369 1732)