The Mysterious Affair at Styles

Invalided home from the front, Captain Arthur Hastings is invited to convalesce at Styles Court, the country estate of his friend's wealthy stepmother, Emily Inglethorp. When she is found poisoned in her locked bedroom, suspicion falls on nearly everyone in the household, and Hastings turns to a chance-met acquaintance staying in the nearby village: a retired Belgian police officer named Hercule Poirot. Agatha Christie's debut novel introduced the world to Poirot, his little grey cells, and the meticulous fair-play puzzle-plotting that would define an entire genre.