During the Dragon Boat Festival, merchants flocked to Bozhou City, and the century-old Wujiang Fish Restaurant was bustling with activity. Li Shanren was distributing zongzi (sticky rice dumplings) to the poor when, suddenly, a black wind arose, and Li Shanren was engulfed in strange flames, instantly turning to ashes. For four consecutive days, four people were burned in four different locations in Bozhou, and rumors of a Gu poison spread, causing widespread fear. Yang Jian, the Prefect of Qianzhou, who had solved numerous cases, happened to be visiting relatives in Bozhou. Curious about the fire Gu poison, he joined forces with Zhao Baozheng, the Prefect of Bozhou, to investigate. After three months, they found a clue through a Miao woman named Hua Adong, but mistakenly entered a secluded Gu village and were trapped by the Gu poison for ten years. It wasn't until Li Yunyi, a third-rank Imperial Guard, was demoted to Prefect of Bozhou and reopened the old case, that they discovered the true culprit behind the Gu poison and rescued Yang Jian and Zhao Baozheng. This strange case became known as the "Ghost Carriage Case."