Set in the historical period of the Joseon Dynasty, the narrative centers on Namsoon (played by Ha Ji-won), a young police officer. Alongside her colleagues, she uncovers a counterfeit operation within the region they are tasked with safeguarding. The criminals are not merely producing fake currency; they intend to use it to destabilize the economy and overthrow the government. During her investigation, Namsoon encounters a mysterious young man known as Sad Eyes (portrayed by Gang Dong-won), whose gaze, partially obscured by his hair, captivates her despite his reticence. Although she knows she should not develop feelings for someone who might end up in prison, Namsoon finds herself drawn to him. Unable to suppress her emotions, she soon begins to act on her attraction, even though it conflicts with her duties.