Sherlock Holmes primarily relies on abduction: inferring an explanation for observed details. "From a drop of water", he writes, "a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other". In "A Scandal in Bohemia", Holmes infers that Watson had got wet lately and had "a most clumsy and careless servant girl". When Watson asks how Holmes knows this, the detective answers: In the first Holmes story, "A Study in Scarlet", Dr. Watson compares Holmes to C. Auguste Dupin, Edgar Allan Poe's fictional detective, who employed a similar methodology. Alluding to
C. Auguste Dupin the three stories, Dupin travels through three distinct settings. In "The Murders in the Rue Morgue", he travels through city streets; in "The Mystery of Marie Rogêt", he is in the wide outdoors; in "The Purloined Letter", he is in an enclosed private space. Dupin is not actually a professional detective, and his motivations change through his appearances. In "The Murders in the Rue Morgue", he investigates the murders for his personal amusement, and to prove the innocence of a falsely accused man. He refuses a financial reward. However, in "The Purloined Letter", Dupin purposefully pursues a financial reward. While