To avoid the summer sun, the Nocturnes head for vacation at Isla Necrata, a resort whose location always changes, putting it near a geologic calamity- most often a volcanic eruption. As a bonus, Oliver is allowed to bring Dean along, the only catch being that he has to pretend to be Oliver's servant. Before they get there, the Nocturnes must endure a particularly uncomfortable visit with Oliver's extended, Old World vampire family, who live in Morosia, a vampire city underneath Rome.

At the same time, Oliver discovers that Emalie has stowed away, believing that Morosia may hold clues to her mother's whereabouts. Oliver must keep his family from finding out about her, sneak out of family obligations to meet up with her on the surface, and search for the oracle that predicted his destiny, which he learns is in the Asylum Colony, somewhere deep beneath Morosia.