Dark Horse by B.M. Bower is the sequel to Chip of the Flying U, the story of cowhand Big Medicine after he saved a stranger on horseback who was struck by lightning. Excerpt: "When Big Medicine saved the strange rider who had been stunned by lightning, he was something of a hero among the cowhands of the Flying U. But not for long. The stranger had amnesia and couldn't remember who he was, so they called him Nameless. He also had been exposed to smallpox. The entire ranch was put in quarantine."