A North Korean killer known as 'Shadow' is sent to assassinate an important dissident who found refuge in Seoul. He is helped by two sleeping agents: Son Tae-soon as look-out, and Song Ji-won, an elite fighter. The North Koreans have not counted with Lee Han-gyoo, from the South Korean National Intelligence Service, who has been tracking them and closes in with his men. Han-gyoo has not counted with the North Koreans' skill and ruthlessness. True to his reputation, 'Shadow' disappears. Ji-won manages to escape, but cannot return to his country, where he is suspected to be a traitor, nor defect, for this means certain death for his wife and daughter who remained in North Korea. Discredited, Han-gyoo is fired from the NIS. Several years later, Ji-won and Han-gyoo meet unexpectedly, and pick up their confrontation -- but not quite from where they left it off.