In Cangjiang City in 1934, Su Yanzhi, a forensic toxicology doctor who studied abroad, returned to his hometown to handle the funeral of his grandfather. As soon as he entered the Su family's century-old house, his grandfather died tragically and locked the study. The only evidence at the scene was a dried black mandala.
Detective Inspector Lu Xun, who was involved in serious crimes in the concession, intervened in the investigation. The case of the Su family's mysterious fire and destruction of the house three years ago was full of doubts. Su Yanzhi accidentally met his twin sister Su Wanning, who looked exactly like him. When they were five years old, they were forcibly separated by the underground drug manufacturing organization Manluotang. The younger sister was placed as an undercover agent in the house of Qin Songnian, a wealthy silk merchant in the city, secretly recording evidence of the organization's crimes.
Manluotang used the Qingxu Temple as a cover, brewed a psychedelic poisonous ointment with the secret Datura herb, colluded with the city defense commander and senior police officials to monopolize gray transactions in the city, and frantically plundered the hydrological jade that the Su family had guarded for generations - the jade contained the flood control drawings of the entire Cangjiang embankment. Once foreign businessmen were lost, the entire city would be flooded during the flood season.
Su Yanzhi relied on skeletal identification and toxicological analysis to solve a series of secret room poisoning plots. He teamed up with Lu Xun, undercover sister, and folk cultural relics guardian Wen Jiuchen to break into the poisonous smoke chamber of the ancient house and destroy the Taoist temple's underground drug production. Workshop, tearing apart the black network of interests of military and political officials and drug manufacturing organizations for many years, finally destroying the poison ointment formula, recovering the national treasure jade for flood control, clearing the Su family of the arson case, and safeguarding the safety of the people of the city and the bottom line of legal principles in troubled times.
