Red herring

A red herring is a plot device used by an author, to trick his or her readers. In the early history of modern detective fiction some authors set up rules, to avoid red herrings.

Red herrings used by Agatha Christie to trick the readers

 * False identification or mixed up identities is used in several stories.
 * The unreliable narrator.
 * A character thought being dead, actually being alive.

Red herrings used within the stories

 * The red kimono in Murder on the Orient Express.
 * The conductor's uniform in Murder on the Orient Express.
 * The name of Nick Buckley in Peril at End House.
 * The killer's plan from And Then There Were None
 * One line of the Ten Little Indians' nursery rhyme ("a red herring swallowed one") which stood for a mistake of the victim, and the survivors believing that he was the murderer (And Then There Were None)
 * The similarity between the names "Lotty" and "Letty" (A Murder is Announced)
 * Unreliable narrator; used in The Murder of Roger Ackroyd and Endless Night
 * Hercule Poirot asking the colour of Ralph Paton's boots; actually wanted to know about who could have taken them from the local pub (The Murder of Roger Ackroyd)