- **The beginning of a mysterious case**: Criminal investigation captain Fu Shenzhou investigates a female corpse that was nailed to a century-old locust tree. The corpse showed a strange smile. Mysterious symbols and fragments of ancient books were found at the scene, unveiling the prelude to a series of bizarre murders.
- **Mysterious Assistant**: Folklore professor Wen Yulu was involved in the case because of her special ability. Her "spiritual vision" ability to see the last memories of the deceased formed a complementary but conflicting partnership with Fu Chenzhou's criminal investigation methods.
- **Death Symbol**: The variant of the "swastika" symbol that appears at every crime scene points to the cult organization "The Society of the Past" that was suppressed thirty years ago, implying that an evil ritual that has been dormant for many years is reviving.
- **Dangerous Alliance**: As the investigation deepens, Fu Chenzhou discovers that Wen Yulu has an unknown connection with the case, and the information she concealed may be the key to solving the mystery.
- **Undercurrent**: Someone within the police station deliberately obstructed the investigation. The mysterious wealthy businessman Cheng Jiuxiao showed unusual concern for the case, and the secret social relationships between the deceased gradually surfaced.
