Hugo Dyson is abducted after Caretakers John and Jack discover a plea for help he has written on a medieval manuscript. Hugo has been taken into the past. As the Caretakers travel back to find Hugo, they finally learn the identity of the Cartographer.

«In this follow-up to «Here, There Be Dragons» John, Jack, and Charles are brought together again after the children of the Archipelago vanish, and the legendary Dragonships, which can cross between the known worlds and the «Imaginarium Geographica» have also gone missing.»