Moonbyul is raised by the mafia and grows up to become a cold-blooded assassin. Moonbyul makes a terrible mistake on mission and is swamped by feelings of regret, guilt and shame, Moonbyul no longer wants to be a killer, but her boss, Jessica Jung, gives her one last mission. So she finds herself in Busan, the land of in which her mother abandoned her, on the trail of her last target. But in bitter irony, that target is Kim Yongsun.