Set in Youcheng, an old city in Linjiang in the south, the protagonist is Shen Yan, the former deputy captain of the criminal investigation detachment. He was forced to resign due to an unsolved case three years ago and opened the "Yanzhi Office" to handle strange cases that are inconvenient for the police to intervene. Youcheng hides centuries-old underground rivers, abandoned republican mansions, closed ancient villages, secret mental hospitals and other strange places. Each case seems to be independent, but in fact it points to Shen Yan's unsolved "Red Rope Hanged Ghost Case" three years ago. After 30 cases, the shocking conspiracy hidden in the city is revealed.
