Great Impersonation

E. Phillips Oppenheim, in full Edward Phillips Oppenheim, (born Oct. 22, 1866, London, Eng.-died Feb. 3, 1946, St. Peter Port, Guernsey, Channel Islands, U.K.), internationally popular British author of novels and short stories dealing with international espionage and intrigue.
After leaving school at age 17 to help in his father's leather business, Oppenheim wrote in his spare time. His first novel, Expiation (1886), and subsequent thrillers caught the fancy of a wealthy New York businessman who bought out the leather business at the turn of the century and made Oppenheim a high-salaried director. He was thus freed to devote the major part of his time to writing. The novels, volumes of short stories, and plays that followed, totaling more than 150, were peopled with sophisticated heroes, adventurous spies, and dashing noblemen. Among his well-known works are The Long Arm of Mannister (1910), The Moving Finger (1911), and The Great Impersonation (1920). (britannica.com)
The Great Impersonation is a mystery novel published in 1920. German Leopold von Ragastein meets his doppelganger, Englishman Everard Dominey, in Africa, and plans to murder him and steal his identity 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. (wikipedia.org)