Deputy U.S. Marshal Jed Colter goes in search of his father, who has been smuggled out of a Union prison camp near the end of the Civil War and placed in forced labor. The journey takes Marshal Colter on a trail that only leads west. Challenged by a blizzard, thunderstorms, and ambushes by Indians and other desperate men, Colter relentlessly pursues his father's captors. As the Union Pacific Railroad rapidly approaches Cheyenne in its quest to join up with the Central Pacific Railroad in Utah, Colter learns there might be more in its cargo than everyone has been led to believe. Ellen Wellsley, a beautiful, raven-haired lady with a troubled past who is unknowingly linked to Colter, provides him with information seemingly connecting the Union Pacific to his father. All the while lurking in the shadows, a young gunfighter stalks Colter and his friend Sheriff Luke Radison. When the mystery man guns down Radison, Colter has to wonder, will he be next?