 Henri Bencolin, of the Paris police, proves that none of these four weapons were used to kill Rose, and that she has been the victim of an unusual fifth.The comings and goings at the villa that night are the subject of much investigation.It is not until Bencolin is invited to take a hand at the Corpses' Club to play a 17th-century game of chance, Basset, that has never been played by any living person, that he resolves the contradictions and solves the crimes.