By the time Christie began writing, the mystery novel was a well-established genre with definite rules. Edgar Allan Poe pioneered the mystery genre in his short story "Murders in the Rue Morgue," and writers like Sir Arthur Conan Doyle carried on the tradition Poe began. In traditional mysteries like Poe's and Doyle's, the story is told from the perspective of a detective-protagonist (or a friend of the detective, like Sherlock Holmes's companion, Dr. Watson) as he or she examines clues and pursues a killer. At the end of the novel, the detective unmasks the murderer and sums up the case, explaining the crime and clearing up mysterious events. As the story unfolds, the reader...