Hyeong-Do (So Ji-Sub) is an assassin for a company that masquerades as a metal trading company. One day, he takes on a job partnering with a man Hyun-Yi, who is he is to kill afterwards. Hyun-Yi asks a favor to Hyeong-Do which is to give money to his family. Hyeong-Do visits Hyun-Yi's home where he meets Hyun-Yi's wife Su-Yeon (Lee Mi-Yeon). Su-Yeon is a former singer whom Hyeong-Do admired in the past. Guilt, an unknown feeling up to this point for Hyeong-Do, begins take over Hyeong-Do.