In five stories between 1840 and 1845, Poe laid out the basics of the detective story, which underlie much hard-boiled fiction. In "Murders in the Rue Morgue," Poe introduced his brilliant, eccentric detective, C. Auguste Dupin, whose solutions were chronicled by an admiring, amiable narrator. Later detectives, notably Arthur Conan Doyle's Sherlock Holmes, became even more eccentric, and Poe's nameless narrator had his counterpart in the amiable Dr. Watson. In "Rue Morgue," Poe introduced three common motifs of detective fiction: the wrongly suspected man, the crime in the locked room, and the solution by unexpected means. Dupin solved the crime by reading the evidence better than the police did and by noticing clues that they had neglected, thus highlighting the importance of inference and observation.
In a second story, "The Purloined Letter," Poe invented the plot of the stolen document, the recovery of which ensures the safety of some important person. Dupin solved this crime by two more important formulae: deduction through psychological insight into the protagonists, and a search for evidence in the most obvious place. In the third Dupin story, "The Mystery of Marie Roget," Poe introduced and developed the crime by recounting newspaper clippings, a technique that later attracted the literary realists and is still used. Though this mystery contained no solution (it was in court at the time), leaving the reader to deduce a solution, it marked the beginning of the genre's use of and competition with newspapers in presenting the "truth about crime" to readers.
Of the other two Poe stories, "Thou Art the Man" presents three important motifs: 1) the criminal confesses when faced with the enormity of his crime, 2) the detective follows a trail of false clues, and 3) he deduces that the criminal is the least likely suspect. In "The Gold Bug," which many think Poe's finest mystery, a man finds an encrypted map that promises the discovery of hidden treasure. All five stories are dark in tone, with characters whose motives are unknowable, as well as the unexpected endings common to the gothic novel in Poe's time.
Poe was also a literary critic, and he created a rationale for the detective story. "The unity of effect of impression is a point of the greatest importance," wrote Poe: "this unity cannot be thoroughly preserved in productions whose perusal cannot be completed in one sitting." 2 Unity of tone and a length that permitted readings in a single sitting led Poe to conclude that detection was essentially a "tale, a species of composition which admits of the highest development of artistical power in alliance with the widest vigour of imagination." Poe suggested three corollaries: 1) Failure to preserve the mystery "until the proper moment of denouement, throws all into confusion, so far as regards the effect intended." 2) Everything should converge on the denouement: "There should be no word written, of which the tendency, direct or indirect, is not to the one pre-established design." 3) It is imperative that "no undue or inartistic means be employed to conceal the secret of the plot." 3 Later writers explored the limits of these rules, but initially they focussed the genre.
1 William Ruehlmann, Saint with a Gun: The Unlawful American Private Eye (New York: New York University Press, 1974), 22. Also valuable is Noel Bertram Gerson (aka Samuel Edwards) The Vidocq Dossier. 2 Edgar Allan Poe, The Collected Works of Edgar Allan Poe (New York, 1965), 14: 358. 3 Poe, 309, 33, 331, 360.