Hercule Poirot is settling in England near Styles Court after being a refugee of the Great War. Styles Court is the country estate of Poirot's wealthy benefactress, the elderly Emily Inglethorp. Authorities are baffled after Emily is poisoned and Poirot puts his prodigious investigative skills to work. There are many suspects, including the victim's much younger husband, her resentful stepsons, her longtime hired companion, a young friend of the family working as a nurse, and a London specialist on poison who just happens to be visiting the village nearby. All of the have secrets they are desperate to hide, but none can outwit Poirot as he navigates a series of ingenious red herrings and plots twists along the way to solve the mystery.