An unexplained break-in in the quiet hamlet of Prescott Lane catches the attention of Dr. Doyle—a man whose morality is debatable but whose curiosity is not. He recognizes immediately that what the authorities have logged does not match what actually happened. The body of an ex-convict found beaten in a dark alley adds urgency. Armed with his straps and a refusal to accept the obvious explanation, Dr. Doyle follows the evidence toward the mystery of the cloche hat.