Ah, Dame Christie. This is the fourth Poirot mystery.
From Library Journal
This novel, written in 1927, is considered the best and most successful of the early mysteries. It met with no small outrage when it appeared, as it uses a plot device many readers thought "unfair." There is a full complement of characters populating the cozy English village of King's Abbot: Major Blunt, Colonel Carter, Miss Gannett, the butler, the housekeeper, the narrator, Dr. Sheppard, and his know-it-all sister (the precursor of Miss Marple, according to Christie), and, of course, the redoubtable Hercule Poirot and his little grey cells. There are clues with a capital C to mislead us, and the listener gets so involved with these red herrings (or not) that the very simple truth eludes the puzzler.A classic of the genre and essential for any fiction collection.