King Sizzeroo, monarch of Umbrella Island, is steering his floating realm through the sky — when he clumsily runs into the giant Loxo, raising a large welt on the giant's forehead. The irate Loxo interrogates the islanders; seeing a boy among them, Loxo demands that the youth become his servant, to lace up his boots. The king and his courtiers are appalled at this — for they known that the "boy" in question is actually the crown princess Reeda. The royal wizard Waddy negotiates a three-month delay before Loxo claims his servant.
In the United States, Speedy and his Uncle Billy are visiting Wyoming, where a paleontologist acquaintance has recently recovered a set of dinosaur bones. The two visitors mischievously try to fit the bones back together. Suddenly a powerful geyser erupts, and sends Speedy and the dinosaur skeleton rocketing into the sky. Some unknown magical force endows the skeleton with life; together, Speedy and the living fossil, known as Terrybubble, are blown all the way to Umbrella island.
The Umbrellians are shocked, at first, by the strange new arrivals; but the newcomers win them over with their youthful high spirits. The king's chief councillor Kachewka develops a sinister plan: noting that Speedy and Reeda look very much alike, he wants to substitute the human outsider for the crown princess when Loxo demands his promised servant.
The Umbrellians all carry umbrellas and parasols, as emergency devices in case the island tips and dumps them overboard; even their domestic animals are so equipped. An attempt to forge a giant umbrella for Terrybubble causes the island to crash into the sea, near the islands of Roaraway and Norroway. The ruler of Roaraway presents an ultimatum: either Umbrella Island leaves the vicinity by ten o'clock the next morning or he will sink it with his water gun. The island, though, is stuck, and needs repair. In a feat of physical courage and endurance, Speedy swims to Roaraway in the night and sinks the water gun to the bottom of the sea with an Umbrellian ray gun. This (along with other acts of resourcefulness and enterprise) wins him the strong admiration of his hosts.
The island is soon back in the sky where it belongs. Terrybubble overhears some of Kachewka's plotting, and realizes Speedy's danger; in an intended rescue, the creature abducts both Speedy and Reeda in their sleep. With the two children tucked into its empty ribcage, Terrybubble jumps off the edge of the island with its giant umbrella, and parachutes to the Land of Oz below. In a stroke of bad luck, the three escapees land at Big Enough Mountain in the Quadling Country, where they are captured by Loxo.
When they realize what has happened, the desperate islanders pilot themselves to the Emerald City, where Sizzeroo and his courtiers appeal to Princess Ozma for aid. The girl ruler locates Speedy and the princess with her Magic Picture, and Ozians and Umbrellians unite in a rescue mission. Waddy brews a magic potion that shrinks Loxo to normal human size, and the two children are recovered, none the worse for wear.
Speedy is tempted to stay in Oz, but his loyalty to his Uncle Billy forces him to return home. He leaves Terrybubble with Reeda and the Umbrellians; the creature lives a pleasant life there, though it misses its former human master.
|Ruth Plumly Thompson's Oz books|