Detective fiction often employs a structure that allows the reader to follow the flow of the narrative through complex plot developments. The structure involves four parts and a midway change, with the sections often called the Introduction, the Discovery, the Midpoint, the Funnel, and the Reveal. Christie was a pioneer and master of this structure.

The Introduction is the section in which the author establishes the characters and setting. The author will introduce the reader to the primary characters, including the victim, the suspects, the detective, and the community where the crime occurs. In The Murder of Roger Ackroyd, the Introduction comprises the first five chapters leading up to the discovery of Ackroyd’s body.

The Discovery phase is the first half of the detective’s investigation. In this phase, the detective conducts the first interviews and gathers as much information about the crime as possible. There will be clues and red herrings that the reader can return to and see how it all leads to the resolution. This section includes Chapters 5 through 11, which describe Poirot and his initial investigation.

The Midpoint is the moment when the detective comes up short. The clues are not adding up, and the case seems unsolvable.