The Purloined Letter

C. Auguste Dupin, the amateur detective from "The Murders in the Rue Morgue" and "The Mystery of Marie Roget" returns for the last time to solve a mystery involving a stolen letter, some blackmail, and the queen. In a series of fortunate and elaborate endeavours, Poe's third detective story is an example of how professionals do not always have all the answers, and that from time to time one needs to think outside the box.
The result is a complex situation that is resolved through clever and rational methods, illustrating Poe's predisposition to mockery and simplicity.