In the land of Green Mane there is treacherous strife. When the Seventh Prince of the Common Lord disappears from the Blue City, the assassin Shadowless is sent to the Blue City to find out the truth.

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.