In the mid-19th century, two brothers, James Howlett and Victor Creed, discover they are mutants with special powers after a traumatic event in their childhood leads James to manifest bone claws from his hands. Driven from their home, they fight together through the American Civil War, both World Wars, and Vietnam, their regenerative powers keeping them youthful and healing their wounds. Their paths begin to diverge when Victor starts to give in to his animalistic side, enjoying the fight and kill too much, leading to a rift between them after a violent incident in Vietnam results in them being sentenced to execution, which they survive due to their powers.

Recruited by William Stryker, who offers them a place in a special team of mutants, the brothers initially join but eventually follow different paths after a mission goes against James’s ethical beliefs, leading him to leave. Years later, living a peaceful life with a new love, his past catches up to him, forcing him back into conflict as he seeks to unravel the truth about Stryker's new project, which involves experimenting on mutants. This quest for vengeance and truth sets him on a collision course with Victor, who has become increasingly unhinged, and reveals dark secrets about their origins, culminating in James undergoing a painful experiment that changes him forever and sets the stage for his future battles, both personal and against threats to the mutant community.