The boy Rio (Jake Schur) is forced to cross the southwestern United States in an attempt to save his sister Sara (Leila George) from his tyrannical (Chris Pratt) uncle. On the other side, the famous outlaw Billy Kid (Dayne DeHaan) is being hunted by Sheriff Pat Garrett (Ethan Hawk). Rio met the two men and witnessed the story of escape, manhunt and struggle between the ratio and the sheriff, and gradually became involved. But in the end, Rio has to make a choice. What kind of person does he want to be, an outlaw or a representative of justice? Besides, how will he save his sister from his evil uncle Papa?