 Hercule Poirot is employed by a young woman named Lucy Crale in order to re-investigate a case that the police closed almost two decades ago. When Lucy was a little girl, her father Amyas Crale, a painter, was murdered by poison and her mother, Caroline, was later found guilty of the crime. Before hanging for the murder in prison, Caroline Crale however wrote a letter to her daughter, professing her total innocence. Lucy Crale now wants Poirot to find out the exact truth about the tragic destruction of her family all those years ago.