Theatre: The eyes don't have it

Throughout Michael Frayn's new play Sara Kestelman wears an olive dress cut just below the knee with chocolate-coloured piping and matching shoes. I tell you this because you could watch Copenhagen with your eyes shut and lose virtually nothing.

In common with many contemporary playwrights, notably Tom Stoppard, whose The Invention of Love began life in this same theatre, Michael Frayn elides historical characters, facts and debate to produce a play of ideas. It's difficult to remember where this vogue for "faction" began, but Terry Johnson made it fashionable in Insignificance, and he vindicated himself with the scene in which Marilyn Monroe illustrates the theory of relativity to Einstein with, if memory serves, a torch, train set and balloon. It must be conceded, however, that even Stoppard's not altogether theatrically riveting play is an evening at the Folies Bergere compared with Frayn's austere three-hander.

The people in question are Nobel prize-winning Danish physicist Niels Bohr (David Burke), his wife Margrethe and his former assistant - and Nobel prize winner in his own right - the German physicist Werner Heisenberg (Matthew Marsh, sounding for all the world like Martin Bell), who formulated the Uncertainty Principle. In his programme notes, Frayn points out that he is not the first person to draw parallels between Heisenberg's discoveries and his life. The connection is made in the biography Uncertainty by David Cassidy, which leads one to wonder if this is the same David Cassidy who recorded the song "How Can I be Sure?"

Frayn's play springs from a disturbing visit that the politically compromised Heisenberg made to his friend in 1941 when Denmark was occupied. History disputes what happened between them, but the two men were separately implicated in the development of atomic fission and the bomb; a return visit in 1947 left the earlier mistrust unresolved.

In order to cloak theoretical discussions about the moral responsibilities of science in dramatic guise, the action takes place after all three have died. The minimal white set appears to take inspiration from the heaven sequences in Powell and Pressburger's fantasy A Matter of Life and Death, and we watch all three "looking for the answers they never found in life". As they repeatedly replay the fateful visit, Frayn uses their hindsight to unravel the secret of what really happened and why, elaborating upon a multiplicity of ideas: the ramifications of Bohr being half-Jewish, his powerlessness at the death of one of his sons, the egotism of research, the influence of politics on pure knowledge.

If strong ideas were all it took to make drama Frayn would be home and dry, but they're only the beginning. He is to be applauded for turning vastly complicated theories into listenable dialogue, but the language he uses to explore their daily lives is undernourished, and, in Michael Blakemore's production, the effect is theatrically arid. Characterisation comes a poor second to theoretical debate, making it a potentially fascinating radio play or, better still, a pamphlet. Freed of the cumbersome devices he invokes to disguise the lack of drama, Frayn's undeniably fascinating ideas would be able to flourish.

`Copenhagen' is in repertory at the Cottesloe (0171-452 3000)