When David Garth returned from America, where his speeches on behalf of the Ministry of Propaganda had caused no small amount of concern, he was surprised to receive an unsigned invitation to an address in Wimbledon.

He was even more surprised when he was approached by two agents of Department Z who were already aware of strange doings at the house in question, possibly aimed at disrupting Anglo-American unity.

But what exactly was going on? Why should David Garth be involved? And why should an apparently motiveless murder be committed?