Accompanying Inspector Japp to Brussels, who is receiving an award from the Belgian government, Hercule Poirot tells him a case from 20 years before. Poirot was a young policeman at the time and at the request of Virginie Mesnard, agrees to investigate the death of rising young politician, Paul Deroulard. The courts had already ruled that he had died of a heart attack, but she believes he was murdered. Poirot believed Deroulard had been poisoned, likely from a box of chocolates he had been given by an aristocrat, Xavier St. Alard. In the end, Poirot identified the killer, even obtaining a confession, but chose not to make it public, for reasons that he explains to his colleagues.