Chicago. Early morning. Beneath the wheels of a bus, a man is killed. His face is so mangled that he cannot be identified, and there are no documents on him. But nearby they find a white box tied with black twine, and inside — a human ear. Detective Sam Porter immediately understands: this is the handiwork of U4O — “The Killers of Four Monkeys,” who has been eluding the police for ten years and continues his hunt in the city. After each murder, he leaves the phrase “Do no evil,” clearly referring to an ancient parable about four wise monkeys. Porter’s intuition tells him that the victim’s belongings — and especially the diary of the maniac himself found among them — are not accidental evidence, but part of a cruel game: mocking clues the killer deliberately uses to taunt the investigation and challenge it…