The Interloper is a thrilling mystery novel written by E. Phillips Oppenheim. The story revolves around the life of a successful businessman named Felix Thurstan, who suddenly finds himself embroiled in a web of deceit and betrayal. Felix, who is happily married to his wife, is shocked to discover that she has been having an affair with a man named Richard Vanderpole.As Felix tries to come to terms with this revelation, he becomes increasingly suspicious...