Six months after the end of The Era of Magic, Rufus is being looked after by his Uncle Seb, helping him to cart tomatoes from his farm to the docks. His parents are missing, having been on a journey aboard The Gumtree - the biggest ship in The Southern Lands - that was attacked and limped home with half the crew missing. Moreover, he feels that his powers as a 'Discerner' have failed, letting down the faith that had been put in him by the Queen.

But then, visiting the restored Gumtree, he is shocked to be chosen, by the ship's trusted cat, as the new Navigator!

He joins up with Kirra, the fisher girl from the first book, and stowaways Clara and Mellek, becoming a vital part of the crew on a voyage that will bring them face to face with what looks to be a revival of the magic: from killer seagulls, to a bombarding forest, to seductive Smiler Fish and knife-wielding weeds.

Can they discover the source of the magic? Is it anything to do with what Rufus has done with the book that tells of the Earth Heart experiment from a year before - a book he was told to destroy? Can they stop the magic and restore balance with the natural world, something the Discerners of the Lands have worked so hard to establish? And, for Rufus the biggest question of all, can they find out what happened to his parents when they disappeared on that last voyage?