The Rubenstein Kiss, Hampstead, London

The suck of death

Named as collaborators by the wife's brother - Alan Cox's David, desperate to save his own skin - the pair stand accused of passing nuclear secrets to the Soviets. Keen and Bond's Jakob and Esther Rubenstein protest their innocence to the end, standing ardently firm.

Spliced with this, two members of the next generation are also depicted, in the Seventies, struggling with the past and reinvestigating the case. They discover their life histories are shockingly closely related.

James Phillips, in his playwrighting debut, has been "inspired by a true story which has been substantially fictionalised". This kind of production note is always worryingly vague. It's not made clear exactly where the facts end and the artistic fantasies start. That said, this is not the first time the real-life cause célèbre of Julius and Ethel Rosenberg - the only US civilians ever executed for espionage - has been worked into fictional frameworks. EL Doctorow's novel, The Book Of Daniel, also envisaged the couple's descendents, looking back on their legacy, with some poetic licence. You might further argue that theatrical pretending reflects the very nature of secret agents. The story is still fascinating. Phillips essentially embraces the evidence which emerged in the Nineties, indicating Julius had indeed been a spy, and Keen injects passionate intensity into his devout Communist speeches about big, beautiful political ideals being more vital, in the long term, than individual lives. As in the Royal Court's recent biodrama, My Name is Rachel Corrie, burning political commitment is presented here with apathy-challenging forcefulness.

The real problem is that Phillips's play - which he has also directed - often rings woefully false in its dialogue, though it has a strong overarching structure. Blatantly sticking his authorial thoughts into characters' mouths, this dramatist hasn't learnt to work undercover. His staging flows pretty smoothly on Liz Ascroft's sparsely furnished set - against a backdrop of decaying tenements. The acting is admirably naturalistic in the main. Keen and Bond both have scenes of heroic stoicism and poignant grief, while Martin Hutson and Louisa Clein, as the 1970's duo, ride through cloying, cutesy exchanges to become interestingly aggressive. But there also toe-curling symbolic moments, not least Bond sexually frotting and sucking Keen's little finger through a prison grille. Phillips has promise but has, frankly, been over-promoted. Hampstead's artistic director Anthony Clark might, once again, have shown better judgement.

To 17 December, 020 7722 9301

k.bassett@independent.co.uk