On her way back from Australia, Dorothy Gale meets her cousin, Zeb Hugson, in San Francisco. They are swallowed up by an earthquake, along with his horse, Jim, and her cat, Eureka, and eventually come down in the Land of the Mangaboos. The Wizard of Oz also arrives there, but the Mangaboos evict them from their country. They take a subterranean journey through the Valley of Voe, are briefly imprisoned in the Land of Naught, and encounter a cavern full of Dragonettes. Eventually they come to a dead-end cavern, so Ozma uses the Magic Belt to bring them to the Land of Oz. In the Emerald City, Jim runs a race against the Sawhorse, and when one of the Wizard's Nine Tiny Piglets goes missing, Eureka is put on trial. Eventually the Wizard is invited to stay in Oz, but Dorothy, Zeb, and their animals decide to return home.