At the beginning of Wu Zhao's reign, the palace maid Qingluan dies of poisoning, and Di Renjie is ordered by imperial decree to solve the case within three days. As he follows the clues, he discovers that the Red Flower Society is conspiring with Prince Wei Wu Chengsi, using the "Thousand-Day Drunk" poison, underground waterways, and a mole within the imperial court to set the capital ablaze with gunpowder during the imperial birthday ceremony and burn down Hanjia Granary. Di Renjie, together with Su Mubai, Ruyan, and others, investigates a series of cases involving charred corpses at Tongque Terrace, nail torture at White Horse Temple, beheadings in the flower market, and a rat infestation at Hanjia Granary. In the end, they save the Divine Capital during a fire that engulfs all four wards and a battle in front of the granary. Xiao Ye fakes his death and escapes, while the mastermind known as "Xian" remains in hiding. Di Renjie is appointed Governor-General of Youzhou and continues his investigation.