"I am convinced that I am in immediate danger and, therefore, I beg you to rush to France".

An urgent plea for help brings Hercule Poirot to the seaside Villa Geneviève, in northern France. However, the ingenious detective does not arrive in time to save his prospective client. Paul Renaud has just been found dead, stabbed with particular ferocity, in a freshly dug grave on the mansion's golf course.

Why is the deceased wearing his son's coat? And for whom was the passionate love letter found in his pocket intended? Before Poirot can answer these questions, the case takes a new, dramatic turn with the discovery of yet another victim, who appears to have lost their life in exactly the same way...