It's a fine day for a sail, and Victor Delahaye Courcy, one of Ireland's most successful businessmen, takes his boat far out to sea. With him is his partner's son, who becomes the sole witness when Delahaye produces a pistol, points it at his own chest, and fires. This mysterious death immediately engages the attention of Detective Inspector Hackett, who in turn calls upon the services of his sometime partner Quirke, consultant pathologist at the Hospital of the Holy Family.