A young boy, Rio (Jake Schur), is forced to travel across the American Southwest in an attempt to save his sister, Sara (Leila George), from his violent uncle (Chris Pratt). On the other side, the famous outlaw Billy the Kid (Dane DeHaan) is being hunted by Sheriff Pat Garrett (Ethan Hawke). Rio meets the two men and witnesses the story of escape, pursuit, and struggle between Billy and the sheriff, and gradually becomes involved. But in the end, Rio has to make a choice. What kind of person should he be, an outlaw or a representative of justice? In addition, how will he save his sister from his evil uncle Papa?