Hyeong-do (So Ji-sub) wears a suit and tie like any other rank-and-file white collar worker... except his profession is murder. Seemingly a section chief in the sales division of a metal fabrication company that is actually a front for an organization of hit men, Hyeong-do is regarded as one of the best contract killers in the business.
One day, he meets a married woman named Su-yeon (Lee Mi-yeon) and instantly falls in love. Feeling guilty about his bloody past, Hyeong-do tries to quit the "manufacturer", to the surprise of his colleagues and his enemies. Seen as the ultimate betrayal, he is immediately hunted down by his former employers.