In the year 1793, 17 years after Jeongjo became the King of Joseon, a series of murders occur. King Jeongjo believes the murders may belong to a conspiracy by government officials to cover up tributary payments. King Jeongjo then gives Detective K (Kim Myung-Min) a secret order to find out who is behind the killings.
When Detective K goes to question the jailed city governor, he discovers that the governor has just read morebeen murdered. Detective K then pulls out the murder weapon: a long metal needle that is jammed into the back of the governor's head. Furthermore, Detective K discovers a clue to the murderer's identity. Remnants of the regional Wolfsbane flower is found near the long metal needle. But, while Detective K is holding the murder weapon, prison guards come into the cell and assume that Detective K murdered the city governor. Now imprisoned, Detective K awakes to find dog fancier Seo-Pil (Oh Dal-Su) standing over him. Seo-Pil helps Detective K escape from prison.
Because of this incident, King Jeongjo demotes Detective K and reassigns him to Jeokseong to investigate the case of a woman thought to have killed herself after the death of her husband. But, this reassignment is more of a rouse for Detective K to get to Jeokseong - the area where the Wolfsbane flower blooms.
As Detective K and Seo-Pil investigate in Jeokseong they come across lady Han Kaek-Ju (Han Ji-Min), who works as a commission agent and controls large groups of merchants. Detective K and Seo-Pil suspect that Han Kaek-Ju and the head of the Noron political party Minister Lim (Lee Jae-Yong) are embezzling taxes to payoff politicians. Meanwhile, Detective K also investigates the case of the woman who reportedly committed suicide after the death of her husband and comes to the conclusion that these two cases are somehow related ...