Millionaire Emily Inglethorp wakes up dead in her room without any sign of violence. Although the police rule out that it is a murder, too many rivalries in the old mansion owned by the deceased suggest a possible case of poisoning that could have gone unnoticed. When Detective Hercule Poirot arrives to take over the investigation, he finds himself face to face with the greed, jealousy, tension and ambition of a family that aspires to inherit a fortune in money and property. An unfaithful husband, her very young lover, envious stepchildren, a strange German toxicologist...? They all seem suspected of having killed Emily, although only one of them may be the murderer. Poirot will have to work hard and use all his weapons to get to the bottom of his first literary case.