A thrilling intellectual mystery, Copenhagen investigates a conversation shrouded in misgivings and unclear memory which may have been the key turning point in the birth of the atomic age.

Playwright Frayn unravels the question of whether German scientist Heisenberg intentionally slowed the Nazi research into nuclear weapons, or whether the Germans lost the race for the bomb simply because he lacked the knowledge to complete it. Having enjoyed an intense and incredibly productive scientific mentoring relationship in which Heisenberg was almost a son to Bohr, they are now divided by the lines of war, and Copenhagen is under German occupation. Heisenberg travels to visit Bohr in order to discuss some pressing issue, the crux of which has been in dispute ever since. Communicating with the knowledge that the Gestapo is listening to their conversations, a nuanced and constant interplay between the language of physics, politics, personality and memory follows.

Frayn shows us various scenarios, changing Heisenberg's motivations in each. This approach is in keeping with Heisenberg's uncertainty principle which declares that we can never know what actually happened to a particle but can only conjecture based upon the observable consequences.

The play is a lesson in physics, history, ethics, and philosophy, and yet is built around the central theme of uncertainty: the uncertainty of the events of that evening in 1941, the uncertainty of right and wrong, and the uncertainty of relationships and motivations. In this framework, Frayn lucidly investigates the minds of two men grappling with the awesome decision of whether to use their knowledge to create nuclear weapons, each knowing that this knowledge, once created, is like a chain reaction beyond one's control.

Though the set is uninspiring, it serves to focus attention on the outstanding text and acting. Stephen D' Ambrose and Katherine Ferrand turn in exceptional performances as Neil and Margrethe Bohr, while J. C. Cutler is strong as Werner Heisenberg.

Brilliantly written, excellently portrayed and well directed, Copenhagen is a play whose many complex intellectual themes could not be more relevant as once again the prospect of nuclear confrontation looms on the horizon. Let us hope that in dealing with the present crisis our national leaders have the same wisdom and intense moral soul-searching that we witness on stage.

Copenhagen Runs January 11-February 9th. Thursday 7:30pm, Friday 8:00pm, Saturday 8:00pm, Sunday 2:00pm, $25-30. Park Square Theatre, 20 West Seventh Place, Saint Paul. Call: 651-291-7005. Park Square's next show, Mary Stewart opens March 1st.