The fictional prosperous Tang Dynasty, with the reign name "Jinghe" (fictitious), appears to be a golden age when all nations came to court and poetry and wine were popular. In fact, there are turbulent undercurrents. Separation of vassal towns is emerging, the dispute between Buddhism and Taoism is intensifying, and the thousand-year alliance between humans and demons is on the verge of collapse. A hundred years ago, the great human race made a covenant with "Baize", the leader of hundreds of demons: demons are not allowed to hurt people without reason, humans are not allowed to kill demons with spirits indiscriminately, and demons can live in "dark alleys" - secret neighborhoods covered by formations in Chang'an City, such as Pingkangli back alleys, Xishi ghost market, etc. The imperial court set up a "siyi prison" to maintain order. A handwritten copy of "Hundred Demons Manual" was circulated among the people, recording the habits, weaknesses and taboos of demons. However, the original copy has long been lost, and most of the copies are fragments or forgeries. The former Supervisor Yiyi died suddenly, and his family was in decline. In order to find out the cause of his father's death, his son Pei Yan got involved in a series of mysterious cases. In the past six months, a series of "broken covenants" have occurred in Chang'an: a noble girl's face was skinned by a painted-skin demon, and her soul was turned into rouge; a kappa in Qujiang Pond stole the dragon's water essence, causing water transportation to be cut off; all members of the camel bell caravan were turned into pottery figurines, suspected of being caused by "terracotta spirits"... Pei Yan met the demon cat A Miao by chance, and made friends to solve the case together and find the mastermind behind the scenes. But the thing was far more terrifying than they imagined, and even affected the fate of the country and the peace of the people. In the end, the mastermind behind the demons was found out, and the war was about to break out...
