Jang Choon-dong is a traffic officer who aspires to become a homicide detective. He is assigned to go undercover to infiltrate a gangster network. Meanwhile, Lee Joong-dae, a member of Kwang-seob's gang, goes undercover himself by joining the police force. Joong-dae tries hard to gain favor with his squad leader in an effort to expose Choon-dong's identity.
Burnt-out transit cop Jay forms an unlikely alliance with pickpocket Kay to stop a terrorist hijacker from blowing up a subway car during rush hour.
Ji-eun, a member of North Korea's dance troupe and the daughter of the North Korean leader, escapes to the South after one of their perfomances. Eager to explore the liberal life in Seoul, Ji-eun searches for a new life of freedom in South Korea. She soon comes across Joon-ho, a leader of a local rock band. Their relationship then takes unexpected turns as they become closer to each other. Meanwhile, the intelligence agency in South Korea learns of a conspiracy being orchestrated by the American CIA to disrupt the peace on the Korean peninsula; the CIA plots to secretly kidnap Ji-eun. Secret forces from the North and South reluctantly agree to work together to prevent a possible war between their two countries.
Sung-chul (Park Joong-hoon), a Korean gangster, flees to Japan after killing a subordinate. On the flight, He-gu (Park Sang-min), an aspiring bartender, discovers his true identity and is forced to act as his guide. Despite multiple betrayals and brushes with death, the two form an uneasy bond. As Sung-chul rises through the ranks of the yakuza, He-gu too is drawn into the criminal underworld. Clumsy but determined, He-gu survives power struggles, betrayal, and heartbreak—only to make reckless decisions that ultimately lead to chaos. In the end, Sung-chul is ordered to eliminate He-gu. At the seaside, after one final plea for mercy, He-gu is shot dead by Sung-chul, who walks away silently.
A man begins a murder spree in a misguided effort to narrow the gap between the very rich and the very poor but when he starts to doubt his mission he finds that he has become addicted to killing and cannot stop.