Tom Horn, Steve McQueen, a legendary frontier scout and tracker who helped capture Geronimo, is a drifter in the disappearing Western frontier at the turn of the twentieth century. The story begins as he rides into a small town and encounters prizefighter Jim Corbett, Steve Oliver. Horn ends up in a livery stable, unconscious and badly bruised, setting the stage for a collision between rugged individualism and the changing moral order of the West.
John Coble, Richard Farnsworth, a cattle rancher, finds Horn and offers him the use of his ranch to recuperate and a job investigating and deterring rustlers who steal from the grazing association to which he belongs. Coble implies that the association will back Horn in carrying out vigilante justice and even receives informal clearance from U.S. Marshal Joe Belle at an association picnic. Horn accepts the offer at the gathering and also becomes acquainted with Glendolene, Linda Evans, the local schoolteacher, forming a quiet bond amid the rough climate of trust and suspicion.
Calling himself a “stock detective,” a label Coble urges him to adopt, Horn confronts cowboys at an auction, giving them fair warning before embarking on a broader, one-man crusade to drive off or eliminate anyone who rustles the cattle of his benefactors. His methods are brutal yet effective, and the rustling problem begins to wane under his firm hand. Yet every victorious action casts a longer shadow, as the public grows uneasy with the violence that accompanies the solution, and the line between hunter and lawman blurs.
A public gunfight intensifies the fear and fascination of the townspeople, and the mood shifts from cautious tolerance to mounting alarm. The powerful ranchers realize that, even though Horn is delivering results, his brutal tactics threaten the region’s image and stability, so they start to plot his downfall. Marshal Belle, who harbors political ambitions, also wants Horn out of the way. The conspiracy gains momentum when a young boy tending sheep is shot by a .45–60 rifle—the same caliber rifle associated with Tom Horn—providing the ostensible motive for his indictment.
Horn is slow to realize that he is being set up. He is warned by Glendolene and Coble to be careful, but he remains stubbornly convinced of his innocence. Joe Belle, who had a hand in shaping the accusations, coaxes Horn from a saloon back to his office, where a newspaperman transcribing their conversation is hidden in the next room. Horn does not admit to the boy’s murder and is incredulous that a shot from his known rifle could reach so far. > If I'd have killed that kid, it would have been the best shot I ever made and the dirtiest trick I ever done. <
Based on that exchange, Horn is taken prisoner. He loses access to the hills he loves, and his world narrows to a claustrophobic town where he cannot move freely. He makes a dramatic break from jail and attempts to flee, only to be recaptured and convicted on the testimony of the newspaperman who skewed the conversation into an admission of guilt. As the moment of execution approaches, Horn confronts his fate with a stubborn pride, maintaining his sense of dignity even as the system closes in. The story concludes with him facing the gallows, resolved in the moments before he is hanged.
