A young woman named Carla approaches the famous detective Hercule Poirot. Sixteen years ago, her mother was convicted of murdering her own husband. Now Carla is about to get married and fears that the affairs of years long past could destroy her personal life. At the same time, she insists that her mother would never lie to her. But back then, sixteen years ago, the mother said she was innocent… Poirot, fascinated by the complexity of the riddle, takes the case—and finds that there are still five people who could be suspected of the murder. And although so much time has passed, and Carla’s mother’s guilt is considered proven, Poirot’s powerful intellect takes up the work…