For only a dollar, Thunder was a terrific bargain. But what can a boy do with a dangerous 2,500-pound buffalo that can break out of any corral ever built?

Nathan Riggins must find some way to keep Thunder from killing someone or being killed. He finally decides to donate his buffalo to the Carson City Zoo. But getting him to the zoo will be a problem. Thunder has already destroyed one rail car and damaged the train's engine. The railroad refuses to ship him again. The answer comes in a surprising way. Meanwhile, there's an exciting contest between Thunder and a prize fighting bull.