Sax Rohmer 
Fire-Tongue 

A London detective is drawn into the web of a deadly cult in this mystery novel by the author of Bat Wing and the Fu Manchu novels.Private investigator Paul Harvey is no stranger to the perils of the Far East, but he is about to encounter a force more deadly than any he has known before. Harvey is visited in his London office by Sir Charles Abingdon, a man he once met years ago in India. Sir Charles believes his life is in danger. But before he can explain his story in full, he suddenly becomes violently ill. And his last words are mysterious indeed: “Fire-Tongue.” The phrase sends Harvey on an investigation that takes him through the shadowy streets of London and reaches across continents. Fire-Tongue is a classic mystery full of nefarious secrets, expert disguises, and deadly twists first published in 1922.