Barnaby finds himself in charge of investigating The Creeper, a man who has been entering peoples homes in the dead of night, after the Chief Constable becomes the latest victim. It all becomes more serious when after one of the burglaries, a man is found dead in his bed. The dead man is David roper, a ghostwriter by profession who was staying with the Chettam family. They had spent the previous evening at the home of Jack Filby who now owned the Chettham estate forcing the family to live in the dower house. Filby and roper had a very loud argument after dinner with Roper, a reformed alcoholic, storming out of the house with a bottle of brandy in hand. He made it back to the dower house and was put to bed. The mystery grows when a second attendee at the same dinner is murdered and the Creeper visits the Barnabys in the dead of night, not to steal anything but to leave behind two clues...