ehearsals for this revival of Michael Frayn’s award-winning 1998 play began last year under the direction of Polly Findlay before being halted. The directorial baton has since been taken up by Emma Howlett and the result is a seamless, energetic production, despite these pandemic bumps. Uncertainty still emerges as the play’s biggest theme. Everything is up for dispute as two leading physicists meet in 1941 to talk clandestinely against the backdrop of a race between Hitler and the allies to create the nuclear bomb. They are on either side of the divide – Werner Heisenberg (Philip Arditti) is a prominent figure in Hitler’s “uranium club” while his one time Danish mentor, Niels Bohr (Malcolm Sinclair), is half Jewish and linked to the US’s nuclear programme. “What did Heisenberg tell Niels?” the play asks, and “What did Bohr reply?” There was no agreement in the memories of the two men and Frayn’s meticulously researched script combines historical record with science-world theories in a drama that drafts and redrafts memory and truth. There are contemporary resonances in its questions around the morality of science, but it is the play’s exploration of the awkward relationship between science and politics that chimes loudest as Covid has brought scientists on to the same public podium as politicians. For Heisenberg and Bohr, there is anxiety and guilt in new science being used for destructive political ends, and both men are implicated. The play still feels maverick in conception, too, seemingly breaking fundamental rules of drama (all talk, no action) while keeping us gripped. Howlett’s dynamic direction creates the illusion of action beyond arguments, ideas and theories, and the pace of the conversation is fast and fluid. The play lends itself to overt theatricality over realism (opted for by Howard Davies in his 2002 film) and it is showcased to full effect, from Alex Eales’s elegant, expressionistic set (spare, with a circular revolve and a giant halo overhead) to its three central characters who exist in a no man’s land of time and space, zipping back to the past from beyond their graves. Both Arditti and Sinclair convey different brands of earnestness and passion, perhaps becoming too stentorian at times but always pulling back from it. Haydn Gwynne, as Bohr’s clever and exacting wife, Margrethe, is vigorous and nuanced. An immediate amicability is sparked between the men so their friendship feels emotionally freighted from the start. The play is about the politics of friendship, too: can these men remain close if they do not share the same politics? Or do their values betray their friendship? While the actors bring an unfaltering energy, their charisma comes up against a barrage of impenetrable science in the second half of the play, which is full of complex physics, covering everything from wave theory and quantum mechanics to scientific community rivalries and the details of the papers the two men write together. This gives an otherwise pacy production some jarringly sludgy moments. The acting stays clear and taut, even if it rises in volume, but this baggy end of the script is more exposed as a result. “Mathematics is sense,” says Heisenberg, by which time he has left some of us behind. The actors never lose us fully, though; rather like a lecture on string theory by Brian Cox, there is charm, even if we hover frustratingly on the outer edges of comprehension. Perhaps most remarkably, it feels alive in its central arguments, proving that complex ideas can – on the whole – keep us on the edge of our seats.