In frontier America at the end of the 19th Century, a confrontation occurs in Colorado that would usually result in a duel to the death. Silas Selleck (Michael Fassbender) is a dangerous drifter who comes across Jay (Kodi Smit-McPhee), a fugitive who has travelled from his native Scotland in pursuit of the love of his life, in the dense and feral forests of the American West. Instead of killing him, Silas offers to protect Jay in exchange for money, and from there they embark on a journey fraught with peril, betrayal and violence.