In his continuing adventures, Twig, now sixteen years old, joins the crew of his father's sky pirate ship and embarks on a dangerous mission to collect the powerful stromphrax, a substance that purifies water and also prevents the city of Sanctaphrax from floating away.

Apprenticed to the Most High Academe of Sanctaphrax, a floating city of scholars, gossip, and treachery, fourteen-year-old Quint runs increasingly dangerous errands, which eventually bring him to a place of gruesome monsters that threaten his life and those of his friends.

Quint finally begins his training at the Knights Academy, Maris adjusts to life in Undertown, and Sanctaphrax shivers in anticipation of a legendary storm, while a storm of a different kind brews between sky-scholars and earth-scholars.

Nate Quarter, a lowly lamplighter in the phraxmines of the Eastern Woods, must flee for his life when the mine sargeant wants him killed, while elsewhere, a storm unlike any ever seen is building.