The Murder on the Links (British Mystery Classic). Agatha Christie

Hercule Poirot and Captain Hastings travel to Merlinville-sur-Mer, France, to meet Paul Renauld, who has requested their help. Upon arriving at his home, the Villa Genevieve, local police greet them with news that he has been found dead that morning. Renauld had been stabbed in the back with a letter opener and left in a newly dug grave adjacent to a local golf course. His wife, Eloise Renauld, claims masked men broke into the villa at 2 am, tied her up, and took her husband away with them. Upon inspecting his body, Eloise collapses with grief at seeing her dead husband. Monsieur Giraud of the Sûreté leads the police investigation, and resents Poirot's involvement; Monsieur Hautet, the Examining Magistrate, is more open to sharing key information with him.