There has been a lot of rumors. It's almost mid-autumn festival, according to the customs, the Crown Prince is going to mourn his deceased mother by the river in the Royal Garden. Guo Changzhi, the Royal Chancellor, is worried about his safety and orders the Da Lisi to solve the case as soon as possible. The Da Lisi, together with Xue Yang, Shangguan Yu and Ding Nai'er, find the murderer behind the case and discover that a huge flesh-eating fish demon which breeds under the Qu River. This fish demon is actually owned by Wu Yantuo–a mysterious yet powerful witch. Because of an earthquake, the fish demon escaped from the cage, which caused the tragedy to occur. The reason for that is actually for the fish to eat up the Crown Prince who was about to become the Emperor. Because this has something to do with the succession to the throne, Xue Yang was vilified and imprisoned. Fortunately, he was rescued by Guo Changzhi and had men secretly sent to assist him. On the mid-autumn night on the Qu River, a man-fish battle stops the plans to murder the Crown Prince....

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In the year 697 AD, Emperor Wu Zetian of the Great Zhou Dynasty orders the grand ceremony of sacrificing the cauldron to be held at the altar near the dam of Guquan Town on the fifteenth day of the eighth lunar month to consolidate imperial power. On the twelfth day, the Dragon God Curse incident occurs at the Guquan Dam, causing many people to undergo physical changes and be devoured and killed by the demonic dragon guarding the treasure of the Dragon God. The Dragon God curse keeps recurring, and what is even more bizarre is that Wang Weihe, a Water Ministry official who has never believed in the Dragon God curse, transforms into a dragon and attacks Emperor Wu Zetian when he goes to court. Di Renjie is ordered to investigate the case and finds that the deceased are all related to the Dragon God treasure under the Guquan Dam. As the investigation deepens, those who are guarding the treasure, such as demonic dragons, Dragon God Sages, and Water-Repelling Pills, gradually surface. With his keen eyes and rigorous deductions, he uncovers a huge conspiracy hidden behind the Dragon God curse. The grand ceremony of sacrificing the cauldron is about to be held, and Di Renjie has to fight to the death to defend the people of the imperial city. However, the reality waiting for him is even more cruel... Should he uphold imperial power or care for the people? Di Renjie struggles through this dilemma....

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