Holmes's addiction to cocaine is developed out of the opening scene of Conan Doyle's The Sign of Four.
In his Introduction, Meyer's Watson declares that "The Lion's Mane", "The Mazarin Stone", "The Creeping Man" and "The Three Gables" (all Arthur Conan Doyle-written adventures from 1927's The Case-Book of Sherlock Holmes) are forged "drivel".