Legendary warrior assassin Yang (Dong-gun Jang) is forced to leave his home when he refuses to kill the last remaining member of a rival tribe - a baby. With his honour in tatters he escapes with the child to the American West, where he arrives in the small town of Lode. There, he encounters a colourful group of circus misfits, including drunken sharpshooter Ron (Geoffrey Rush) and knife-throwing Lynne (Kate Bosworth).
However, there is no respite for the warrior, who becomes embroiled in Lynne's revenge mission against the murderous Colonel (Danny Huston). It is only a matter of time before Yang's past catches up with him. His mentor, Saddest Flute (Lung Ti), and a lethal gang of cloaked assassins arrive in town, intent on taking the lives of both Yang and the infant he protects.
Aided by the motley crew of circus performers, Yang is forced into an epic battle to defend his ward, and to finally be rid of the past that has haunted him.