Oppenheim, E. Phillips: The Great Impersonation, v1. 05 Feb 2011
This is a spy story by an author which seems to have written thrills of every genre.
An English baronet and a German baron share: appearance, schooling, years in Africa away from their friends, and mysteries in their separate pasts. And World War I is impending... Moreover, each of them has a woman in his life - which provides added trouble for impersonation purposes.
The text comes from Project Gutemberg and the images from the Internet Archive.
Corrected and formatted, thanks to Calibre and Sigil.