The play starts in a fairly natural mode.
Heisenberg arrives at Niels Bohr's house and it's a very embarrassing meeting because Bohr did not want to be visited by a German in 1941. He did not want to appear to be collaborating. Heisenberg plainly wanted to say something to Bohr or he wouldn't have insisted on the meeting.
The play begins with this very awkward conversation between them and then they go out for a walk. Something goes wrong with the conversation, we don't discover what, but they come back to the house and Bohr says Heisenberg's leaving.
Then the characters try to reconstruct what it was that was said during the walk, which they never agreed about. And they do three drafts of this. They go through the conversation three times before they come upon some sort of explanation of what was happening.
It never occurred to me when I was writing it, but some interviewer pointed it out afterwards, that it was the same structure as an earlier play of mine called 'Noises Off.' 'Noises Off' is a farce about the theatre and we see the same actor in the same play three times over.
I seem to be plagiarizing my own structure.