Robert Turold had spent his life trying to prove his claim to an ancient title. Yet, when it seems he is about to finally succeed, his body is found in a remote cottage on the Cornish coast, an apparant suicide. When his sister expresses her doubts to the police, Scotland Yard is called in and agree that it is murder. But the room where the victim was found was locked and faced a perilous cliff overlooking the sea. Who then killed Robert Turold? His daughter, who he was planning to disown? His brother who stands to inherit? The mysterious servant? Find out in The Moon Rock!