The Great Impersonation (1920) by

The Great Impersonation is a mystery novel written by E. Phillips Oppenheim and published in 1920. German Leopold von Ragastein meets his doppelganger, Englishman Everard Dominey, in Africa, and plans to murder him and steal his identity in order to spy on English high society just prior to World War I. However, doubts of the returned Dominey's true identity begin to arise in this tale of romance, political intrigue, and a (literally) haunting past. The story begins in German East Africa, where Englishman Everard Dominey awakens to his doppelganger host, German Leopold von Ragastein. They spend the night drinking and sharing their dark pasts. The next day, Leopold and Dr. Schmidt hatch a plan to make Everard disappear in the wilderness, thereby allowing Leopold to steal his identity and fulfill his special commission for the German government.