Set in the late 19th century, The Last Son centers on LeMay (Worthington), a murderous outlaw who learns from a soothsayer that he is cursed by a terrible prophecy: that he will be killed by one of his sons. To prevent his own death, LeMay tracks down his spawn, whose bloodlines are confirmed by a hereditary birthmark, eventually finding his son Cal (Machine Gun Kelly), who himself is on a murdering rampage. With bounty hunters and the enigmatic sheriff Solomon (Jane) on their tail, LeMay must find a way to stop his son and end the curse, with the two set on a collision course toward a brutal game of cat-and-mouse.