Referred to as Faber throughout the novel, this character has many names because of his work as a spy. Faber is the antagonist of the novel. As a spy, Faber keeps his life isolated, not making friends or other attachments because anyone who knows him might discover his espionage and betray him. An example of this self-protective isolation takes place in the first chapter when Faber kills his landlady when she enters his room without permission and sees the wireless radio transmitter he was using to send a message to Germany. Faber makes the murder look like a sexual assault and moves on to another part of London, escaping the area without anyone missing him for several days. This isolation is an important part of Faber’s work, but it will later take a toll on him, making him vulnerable when he develops romantic feelings for Lucy at the end of the novel.

Faber appears cold and calculated throughout the novel, focused only on his loyalty to his country and his determination to help Germany win the war. However, each time Faber commits a murder, he becomes physically ill. While Faber himself puts this down to nothing more than a nuisance, it shows a more human side to his character, exposing a vulnerability that suggests he has more of a conscience than his behavior suggests.