A timid man is the butt of practical jokes in a boarding house. He likes the proprietors' daughter Nancy, and she encourages him to stick up for himself, but he can't find the will or the strength. Then, he reads about a scientific breakthrough: a doctor has found a way to inject the personality of a bulldog into timid humans. He volunteers for a treatment, and soon he's storming toward the boarding house to put his tormentors in their place. Will he succeed or will something in the nature of things keep him living a dog's life?