In the old buildings of Huai Listening Lane in South City lies a paranormal detective agency that specializes in solving supernatural mysteries. Yun Xi, its silver-haired, odd-eyed director, can use her red eye as a key to enter dreams and explore souls, and guide the dead onward. The patterns formed by her red eye can also track spirits and open a passage to reincarnation. Lei Ze, a demon-slaying warrior with a pure yang constitution, fights evil with his long sword alongside Lei Cheng, a zombie companion who is the embodiment of their ancestral master. The agency is also protected by Yun Jin, a fox spirit who can take human form, and Yun Ling, a black cat who transforms into a little girl.
Grief-stricken Li Ming comes to beg them to guide the spirit of his dead wife, Zhao Lili, but the case exposes a shocking conspiracy: Zhao Lili’s organs were stolen after her death, and behind it all is a collusion between the Soul-Eater Club and the Ghostbone Alliance. The former is controlled by the evil mage Wu Shi, who uses contracts to lure elites from all walks of life into selling their souls, then possesses their bodies to prolong his life. The latter trades organs through the dark web, moving victims from South City overseas in a bid to turn the city into a spy base.
The agency is attacked, and Yun Xi’s red eye is sealed. At the brink of despair, Lei Ze uncovers an ancient secret of the Lei family: the union of yin and yang. Using an ancient artifact, he awakens the power of fusion. In the end, Yun Xi and Lei Ze crush the Soul-Eater Club, then join forces with police captain Shen Xiuwen to destroy the Ghostbone Alliance, allowing countless restless souls to find peace. But just as the turmoil subsides, a new commission arrives, and more secrets of the worlds of yin and yang await discovery.
