Set in the late 19th century in Wyoming, the story follows Harvard graduate James Averill who becomes a marshal in a small town known for its significant immigrant population. The settlers, mainly poor immigrants, are struggling to establish their lives against the economic control exerted by wealthy cattle ranchers. When the powerful Stock Growers Association, headed by Frank Canton, compiles a death list targeting 125 immigrant settlers over suspected cattle rustling, tension boils to the brink of violence. The Association hires a band of mercenaries to carry out the assassinations, placing a bounty on each settler's head. Averill, disillusioned by the disparity between the social classes, empathizes with the settlers and decides to intervene.

Parallel to the main conflict, a love triangle emerges involving Averill, Nate Champion, a hired gun working for the Association, and Ella Watson, a local bordello madam who has a romantic relationship with both men. As Averill becomes more deeply involved in the settlers' plight, the stakes grow higher, and the conflict with the mercenaries becomes inevitable. The town's struggle against the oppressive reach of the cattle barons, alongside the intricate personal dynamics, pulls Averill into a violent and morally complex confrontation, forcing him to face hard choices about loyalty, justice, and survival.