Sax Rohmer 
Bat Wing [EPUB ebook] 

Knox and Paul Harley are speaking while seated in Paul Harley's office. In addition to being a private investigator, Harvey advises the British Empire's political establishment. When Colonel Juan Menendez enters the room, the two are discussing what position Paul should adopt next. Paul thinks that his fear of being pursued by someone is just delusion. Menendez has only ever seen the shadow of the person, but he is nevertheless certain that they are watching him. Then Menendez reveals a bat wing that had been left for him. Harley is then abruptly thrust into a world of voodoo, vampires, and murder!