The novel's central irony: the judge is the murderer. Wargrave is introduced as a hanging judge with cold, pale eyes and a lifetime of sending men to death — the reader perceives him as a morally weighty authority figure, not a suspect. His confession reveals a man of genuine intellectual distinction who has merged two obsessions — justice and death — into a single act. He is not a monster. He is a man who decided that his judgment was better than the law's, then acted on that decision with complete rationality. This makes him far more frightening than a monster would be.