In a rigged gunfight Tom Blake is forced to shoot a man in self defense and is then hunted for murder. After a long trip fleeing the posse he uses a false name and joins the Pony Express which is just about to commence operatons. Relegated to the most dangerous section of the route, he finds himself fighting the District Manager's scheme to sabotage the inital run. But just then a wanted poster with his picture on it arrives.