The Double Traitor is an espionage novel set in the days leading to the first World War. The main character is Francis Norgate, an aspiring British diplomat who falls in disfavor with his superiors for defending a woman while stationed in Berlin.
On the way home, he meets a German gentleman, Selingman, who claims to be a crockery salesman. Oppenheim tells a good story a little romance, a little adventure turn of the century tales of success and failure, gain and loss.
