The six stories in Part I of this book trace the early career of Peter Benskin. He is a public school graduate with a small private income who joins the police force in London. After an early success he transfers to Scotland Yard where he becomes a detective. He is successful in solving several difficult cases but is hampered at times by his ethical feelings towards criminals who have been coerced or forced to commit crimes. He allows the „innocent" to escape, while he pursues the „truly" guilty. Part II of the book, which also consists of six stories, chronicles Benskin's pursuit of and ultimate victory over a self-conceited master-criminal known only by the sobriquet „Matthew".