At the end of the Yan Dynasty, there was an imbalance of yin and yang, and the undead were in chaos. Xiao Yan, the underworld pen clerk, went down to earth with the "Yin Division Pen" that can record the memories of the dead, and solved a series of supernatural cases such as "wrongful souls in ruined temples", "evil spirits in ancient tombs", and "royal secrets". On the way, he joined hands with stargazer Shen Xingyao to gradually uncover the revival of the cult "Youming Sect" and its conspiracy to break through the yin and yang world to destroy the human world. Ultimately, the cult's plan was defeated and the order of yin and yang was maintained.
