Though The Ice is receding as the next Ice Age ends, much of Earth remains frozen, and the vast Ice Sea has its pirates, among them the notorious and notable Captain Lork, who profitably raids mountain peak towns in the far North. Through grievous misfortune, during their exploration of the Ice Sea, the twin brothers Thist and Thusk and their flying machine, Una, are captured by Captain Lork. The two wildly different cultures, previously unknown to each other, must then adapt to their knowledge of new worlds. Eventually, many travel back to Motherland, where unexpected romance and palace intrigues await them--rebellions, betrayals, corruption, wars, death-until all the main players on Earth and Moon arrive at unexpected destinations and circumstances, each going their own way, drastically changed by their common experiences.