Twins Annalie and Will Wallace return in this action-packed sequel to the stunning cli-fi novel The Flooded Earth

It's been months since their father, Spinner, disappeared after the Admiralty tore apart his workshop and sent him into hiding, but Annalie and Will are determined to find him, whatever the cost. With the help of new friends Essie and Pod (and talking parrot, Graham), the siblings use the decoded clues Spinner left behind to track his movements, sailing around the world in search of his old scientific colleagues.

But the Admiralty is still in hot pursuit, and the sea might be the biggest threat of all. As the children battle massive storms, menacing marines, and pirates out to steal anything (and anyone) they can, the twins and their friends discover new levels of strength, determination, and ingenuity within themselves. They also begin to wonder if they'll ever catch up to Spinner, or if the dangers they encounter along the way will seal their fates first.

The Castle in the Sea is the sequel to the 2019 Green Earth Award-winning novel The Flooded Earth