[2] The two main characters, both fictional, are Hugh Legat, private secretary to Neville Chamberlain, and Paul Hartmann, a German junior diplomat and member of an anti-Hitler group.

Legat and Hartmann are friends from their student days at Balliol College, Oxford University.

[1] On 21 September 2017, an article in the Evening Standard asserted that the Paul Hartmann character was based on Adam von Trott zu Solz.

[3] Hartmann, like von Trott zu Solz, is executed by hanging as a member of an anti-Nazi conspiracy during World War II.

His fictional counterpart Legat dies many years later as an honoured civil servant.