Did he stop the Germans from producing their own nuclear bomb - or was he a Nazi sympathiser? Michael Frayn's fascinating, scintillating philosophical teaser about the German physicist Werner Heisenberg's visit in 1941 to his Danish mentor, Niels Bohr, and its possible consequences posits the question as only one of many in one of the most intellectually thrilling plays of the decade.

Imagine Stoppard on speed. Imagine a physics and philosophical lecture in which you are dragged into the very nucleus of debate on the nature of the atom - nuclear and human. What are the motivations that lie behind man's insatiable drive for knowledge and whither will it take us? To oblivion, suggests Frayn through the mouth of Bohr, the father of fission, in a play that explores the impact of human behaviour and personal motivation on pure ''abstract'' thinking to breath-taking effect.

With the timing, as so often, eerily coinciding with public events (the resurgence of the nuclear arms race in Asia) Frayn's play could hardly be more pertinent - or Michael Blakemore's production more impeccable.

Peter J Davison's built-up back wall turns the square-boxed Cottesloe into a hermetic rotunda housing just three characters - Matthew Marsh's urgent, ambiguous acolyte, David Burke's paternalistic Bohr, and Sara Kestelman's eagle-eyed Margrethe Bohr missing nothing.

A tale of memory, friendship, loss, responsibility, the male/ female equation, history, and so much more (Heisenberg was credited with the formulation of the scientific theory known as The Uncertainty Principle) the cry of ''but this is a radio play'' will undoubtedly be heard in some quarters. In reality the impact of watching these three reacting on each other is nothing less than explosive. Fabulous.