Hercule Poirot receives an urgent appeal from Paul Renauld, a wealthy businessman who fears for his life, and travels with Hastings to the French resort of Merlinville. They arrive after Renauld has been stabbed and left beside an unfinished grave on a golf course, while his wife describes a night-time attack by masked intruders.
The inquiry uncovers competing identities, a crime from an earlier generation and a second plot that intersects with the first. Poirot’s psychological method is challenged by the confident forensic approach of the French detective Giraud, while Hastings’s attachment to a young performer complicates his loyalties. The novel uses the mobility and new wealth of the 1920s to connect English respectability with secrets preserved across borders.