Poe gave "The Murders in the Rue Morgue" an unusual form. He begins the piece as an essay and then offers the story of the murders as an example of what he has discussed in his essay.
The narrative which follows will appear to the reader somewhat in the light of a commentary upon the propositions just advanced.
"The Murders in the Rue Morgue" begins with the following sentence:
THE MENTAL FEATURES discoursed of as the analytical, are, in themselves, but little susceptible of analysis.
So it is the analytical powers of the mind that Poe, through his anonymous narrator, discusses in detail before telling about how he came to meet and share "a time-eaten and grotesque mansion, long deserted through superstitions into which we did not inquire," with C. Auguste Dupin and then finally describing how they both became involved in the murders of two women in the Rue Morgue in Paris. The narrator spends a great deal of time discussing the games of draughts (checkers) and chess, making the controversial assertion that checkers is a far more difficult game than chess. He then goes on to discuss how superior analytical powers can be used in the game of whist. He subsequently introduces C. Auguste Dupin as a supreme example of a possessor of great analytical powers. He still says nothing about the murders but gives several examples of Dupin's powers.
At such times I could not help remarking and admiring (although from his rich ideality I had been prepared to expect it) a peculiar analytic ability in Dupin. He seemed, too, to take an eager delight in its exercise—if not exactly in its display—and did not hesitate to confess the pleasure thus derived.
Dupin's most impressive display of his analytical powers before the murder investigation occurs when he amazes the narrator by telling him precisely what the narrator has been thinking, for at least the past fifteen minutes, as the two men are taking their evening walk. Both men have been silent until Dupin says:
“He is a very little fellow, that's true, and would do better for the Théâtre des Variétés.”
“There can be no doubt of that,” I replied unwittingly, and not at first observing (so much had I been absorbed in reflection) the extraordinary manner in which the speaker had chimed in with my meditations.
Finally, the narrator offers the whole story of the investigation of the murders of two women in a locked room as just further example of Dupin's phenomenal analytical powers. Dupin was a direct forerunner of Sherlock Holmes, and Dupin's powers can perhaps be better understood as being about the same as those of his more famous follower. Poe was a far greater genius than Arthur Conan Doyle. Poe experimented with what he called "tales of ratiocination" and then grew bored with them and went on to entirely different projects. Doyle, on the other hand, wrote four Sherlock Holmes novels and fifty-six Sherlock Holmes short stories, and they made him rich and famous.
It should be noted how "The Murders in the Rue Morgue" proceeds from a dispassionate discussion of the subject of so-called analytical powers to a fantastic scene, described by the sailor, in which an orangutan is attempting to shave the face of a terrified old lady with a straightedge razor. The contrast between the essay and the description of screaming women covered with their own blood is what makes the climax so effective.