It is September 1941 and young Freddie Hackett is a message runner - he collects messages from a government office and delivers them to various destinations around London. On this particular day, he sets off with his message, along a route of bombed out houses and heaps of rubble, and comes across two men violently arguing. He rushes into the doorway of a bombed house and tries not to be seen - but from his vantage point he witnesses a murder.

After the killer goes on his way, Freddie finally comes out of hiding, but he has an envelope to deliver and all messages from that office are urgent. He arrives at the house and he could swear the man who answers the door is the very man he has just seen kill another. But is he? Freddie flees, and reports what he has seen to the police but they brush him aside. It is then he remembers delivering a letter to Maisie Dobbs, a private investigator in Fitzroy Square - perhaps she will believe him and help solve the mystery?