On the occasion of the birthday feast of Queen Wu Zetian, it was suddenly reported that the "red-eyed monster" was committing a chaotic case, and Wu Zetian ordered Di Renjie to supervise the case. Di Renjie and his apprentice Chen Jiangqiao came to Fangzhou to investigate the case, and chanced upon Shen Qingqing, who was also investigating the case. Through the investigation of the case, the trio gradually approached the truth behind the "red-eyed monster", which led to a series of serial incidents. In the process of dealing with this series of incidents, Di Renjie was upright, putting the common people of Li people first, and expressing a sense of responsibility and mission that "everyone is responsible for the rise and fall of the world", and finally successfully solved the mystery.

The movie tells the story of Chang'an City, which was instantly flooded by a sudden dense fog, and the people panicked and fled everywhere. The unscrupulous Xiao Cheng guards the weak prince and is trapped with the civilians, waiting for the fog to dissipate. However, the fog did not disperse as expected, and the people who walked into the fog never returned. The fog gradually revealed the hideous face of the frightening beast, and Xiao Cheng fought to his death to protect Chang'an