THEATRE Twilight of the Golds Arts Theatre, London

Would you abort a child if you knew it was gong to be gay? Nobel Prize-winning scientist, Dr James Watson, recently told Sunday Telegraph readers that "if you could find the gene which determines sexuality and a woman decides she doesn't want a homosexual child" then this would be grounds for a termination. First seen on Broadway in 1993, Jonathan Tolins's play, The Twilight of the Golds, imagines a scenario in which a wife of a research geneticist discovers, through testing, that the male foetus that she is carrying will most likely be gay. The play, which sometimes makes you squirm as much as it makes you think, looks at the turbulent effects of this knowledge on the kind of suffocating New York Jewish family (all worries and wisecracks) beloved of Broadway comedy.

Each of the five characters is allowed to button-hole the audience with a confessional monologue, but our main guide is the pregnant woman's brother, David, a gay theatre-designer (attractively played by Jason Gould). This cultured, sweet-natured, well-adjusted charmer is key both to what is best in the piece (it's exposure of the homophobia that even a loving, liberal family can unconsciously harbour) and to what is worst (the needlessly operatic uplift of the case it makes for human diversity and its failure to give due weight to the fact that there are honourable reasons for being anxious about launching a gay child into a prejudiced society).

David takes the line that in contemplating an abortion, his sister Suzanne (whose whingeing spoiltness is finely captured by Gina Bellman) is effectively questioning the validity of his own existence. What would his conventional parents (Sheila Allen, Peter Laird) have done? A passionate outburst from his flustered father reveals that if there was a cure for homosexuality, he'd want David to take it. His mother, who is ashamed at having allowed herself to lose touch with a close friend diagnosed as having a genetic disposition to Huntingdon's disease, doesn't want her daughter to make a comparably self-protective, life-denying mistake. She can't voice her feelings directly, though, because she knows that if testing had been available she would have aborted her son.

The uncomfortable contradictions in the family's treatment of David, who is at once adored and (as he now sees) underlyingly tolerated rather than fully accepted, is well conveyed in Polly James's slightly tentative production. Can it be him they love, if they'd be happy to see a crucial part of his identity wiped away?

Played on a witty set by Tim Shortall that brings Wagner's mountainous peaks into a conventional New York apartment, Twilight ventures shaky parallels with The Ring as the Golds find themselves in the predicament of having to make god-like choices. The idea of aborting a foetus because of its sexuality is, to my mind, inherently disgusting. But to counter it you don't need to pump up the stakes with the suggestion that Suzanne would be giving birth to a second Siegfried, a beautiful hero, who could prove, in marching unhurt through the flames, that what we have been taught to fear is a fraud. "There's greatness in you, Suzanne Gold. Awaken. Usher in a new era," David portentously beseeches her. But Siegfried was also the puppet of his own ignorance and came to a very sticky end. Question: Would you abort a child if you knew it was going to be Siegfried?

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