The series is situated in 1990s Seoul, where a former DJ becomes a key player in the illicit drug trade, peddling a potent substance known as “Gangnam Crystal” within the city’s vibrant nightclub scene. As this dangerous drug gains prominence, with law enforcement clueless about its origins, the task of dismantling this flourishing drug trafficking syndicate falls to Park Jun-mu, a rural police officer who is entrusted with infiltrating the organization.