Superstition.

Will Clayton is superstitious. He is ridiculed for his superstitions, fired for them, gets involved in a murder mystery, is captured by bandits, despised by the girl, but he clings to his amulets and his horseshoe. Finally, when the girl agrees to marry him if he throws away her silly amulets and horseshoe, he takes her in his arms, throws a horseshoe out the window, and it knocks the gun out of his rival's hand just as he is about to shoot.