The famous detective Hercule Poirot is approached by a young woman named Carla, whose mother sixteen years ago was convicted of murdering her own husband. Now Carla is going to get married and fears that the affairs of long past years can destroy her personal life. She said her mother would never lie to her. And she said sixteen years ago that she was innocent... Poirot, fascinated by the complexity of the mystery, takes up the case and finds out that five more people can be suspected of murder. And although so much time has passed, and Carla's mother's guilt is considered proven, Poirot's powerful intellect takes up the job...