Saint Marie's governor, Caroline Bamber, is killed at her going-away party in the house's back garden. Her champagne, handed to her by Commissioner Patterson, was poisoned with cyanide. Suspects include her staff and the French governor of nearby Saint Robert who is disputing the ownership of a small island, Spinner's Rock, claiming it to be French and not British. The secret of the island, love, death, greed, revenge, or a new road round a village could provide a clue.