When the future empress Wu Zetian's two courtiers die in a mysterious fire, she gets Di Renjie, a former detective and rebel, released from prison to solve the mystery of the fire.

Young Dee Renjie arrives in the empire's capital to join the Supreme Court as police judge of his region. He wants to become a prosecutor. Empress Wu, who is at the beginning of her reign, has commissioned the fierce detective Yuchi to investigate a sea monster that stalks the city at night and makes it unsafe.

Dee, the detective serving Chinese empress Wu Zetian, is called upon to investigate a series of strange events in Loyang, including the appearance of mysterious warriors wearing Chiyou ghost masks, foxes that speak human language and the pillar sculptures in the palace coming alive.