Lee Ja-Sung is an undercover police officer who has been working in Goldmoon International, South Korea's largest corporate crime syndicate. During his 8 years, he is constantly at risk of discovery. Chief Kang
promises to reassign Ja-Sung to an overseas position in the police force, but he continually delays his promise. When Ja-Sung threatens to quit the police force, Chief Kang threatens to leak his true identity to the crime syndicate, which would ensure his painful death.
The chairman of Goldmoon dies in an accident, and two men fight to see him. Jung Chung is backed by the Chinese-descended Northmoon clan. Lee Joong-gu is backed by the Jaebum faction.
Chief Kang sets Jung and Joong-gu against each other in hopes that they will defeat each other and clear the path for Jang Su-Ki to become the new chairman. Su-ki is nominally the vice president of the company, but he has no real power. Chief Kang hopes that the Goldmoon company will be weak enough to defeat if led by the weak Su-ki. Chief Kang blackmails Jung and convinces him to leak evidence about Joong-gu in exchange for a pardon for his own crimes. After he arrests Joong-gu, he informs Joong-gu that Jung betrayed him. Enraged, Joong-gu sends his men to assassinate Jung. Joong-gu's men ambush Jung and fatally wound him. In the meantime, Joong-gu's men break into Ja-Sung's house. Ja-Sung's wife is saved by the police but suffers a miscarriage from shock.
Shattered by Jung's attack and terrified of what Joong-gu will do to him once he is released from prison, Ja-Sung begs Chief Kang to reassign him and let him disappear. Chief Kang refuses to keep his promise and destroys Ja-Sung's police profile to force him to continue to work for Goldmoon. After that Ja-Sung goes to see Jung at the hospital and, before his death, Jung tells Ja-Sung to decide his loyalty. Ja-Sung understands that Jung discovered that he is an undercover cop, but he pretends not to know because of their friendship.
Ja-Sung finally decides to become a full criminal. He takes control of Jung's faction and secures the loyalty of Su-ki's men. He murders Su-ki, who is set to become the chairman because of Chief Kang. He murders Chief Kang so that no record will remain of his old identity. He murders Joong-gu, his only possible rival, to become the new chairman of Goldmoon.