The crumbling Farningcote Priory has been the home of the Glapthorne family for generations. In the grounds stand a tower, built as a folly during the eighteenth century which seems to have a strange, almost mystical power over the family. When Caleb Clapthorne is killed in what at first appears to be a shooting accident, it soon proves to be murder. Yet Inspector Waghorn, in the area on the trail of a gang of thieves but called in to assist, fails to find any obvious motive. In the end he turns to Priestley to track down the vital clues.