The Mysterious Affair at Styles Agatha Christie

A refugee of the Great War, Poirot has settled in England near Styles Court, the country estate of his wealthy benefactor, the elderly Emily Inglethorp. When Emily is poisoned and the authorities are baffled, Poirot puts his prodigious sleuthing skills to work. Suspects are plentiful, including the victim’s much younger husband, her resentful stepsons, her longtime hired companion, a young family friend working as a nurse, and a London specialist on poisons who just happens to be visiting the nearby village.