 Special agent West is charged with the responsibility to transport the state s only supply of a smallpox vaccine to safety. On the way, West s stagecoach is ambushed by a gang, led by Silas Crotty, who steals the serum and shoots West as he tries to protect the vaccine. When West awakens in the field, he has lost his memory and his identity, not even recognizing Artemus Gordon who is trying to rescue him.