It has been nine years since John, Jack, and Charles had their great adventure in the Archipelago of Dreams and became the Caretakers of the Imaginarium Geographica. Now they have been brought together again to solve a mystery: someone is kidnapping the children of the Archipelago. And their only clue is a mysterious message delivered by a strange girl with artificial wings: 'The Crusade has begun.' Worse, they discover that all of the legendary Dragonships have disappeared as well.