During the Yongping era of the Great Yin dynasty, beneath the splendor of the imperial capital lurks a book that strikes terror into all who hear of it: the Book of Forbidden Rules for the Xu Hour. Its pages contain neither gold and silver nor secrets of the court, but one blood-written, incomprehensible rule after another. At a quarter past the Xu hour, the evening drums sound, the city gates are locked, and the wards shut their doors. Then this thin booklet quietly appears beside the pillows or on the desks of certain people, or even brands itself directly into their minds. Its rules are absurd and uncanny: "At a quarter past the Xu hour, do not light a lamp to look at your shadow." "If you hear someone call your name from behind, do not turn around." "When the moon is full in the well, do not draw water." "If you see a woman in red at the end of an alley, scatter white rice along the road"... Those who break the rules may go mad or lose their souls at best; at worst, their flesh and blood vanish, leaving behind a horrific and bizarre death, as if swallowed by an unseen "taboo." Shen Yan, a destitute scholar burdened with the "Night Eye," which lets him see what ordinary people cannot, is accidentally drawn into this mystery. To protect himself and uncover the truth behind his close friend's bizarre disappearance, he is forced to travel with Liu Qixian, a mysterious mute woman, and embark on a thorny path to survive the taboos of the Xu hour. They must not only unravel one deadly rule after another, but also fight the uncanny entities lurking in the darkness, gradually exposing the earth-shattering secret behind the Book of Forbidden Rules for the Xu Hour, one capable of toppling a dynasty and overturning the balance of yin and yang. As an ancient curse intertwines with the shadow of imperial power, and the boundary between life and death blurs in the Xu hour's tolling bells, can they find a glimmer of hope amid countless taboos?
