In 1782, 16 years after Jeongjo became the King of Joseon, a series of murders occurs. 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.Detective K: Secret of Virtuous Widow 2011 Movie.
When Detective K goes to question the jailed city governor, he discovers that the governor has just been 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 are 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 ruse 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 Im (Lee Jae-yong) are embezzling taxes to pay off 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.