Since accidentally joining the crew of pirate ship the Onion, the lives of twelve-year-old Brine Seaborne, her magician friend Peter and former-librarian Tom have been turned upside down. Having battled the world's most evil magician, Marfak West, fought off sea monsters, and found Magical North, they thought they were prepared for whatever the eight oceans could throw at them . . . until they hatched the world's last known dragon.
Desperate to find a family for their fire-breathing friend and hoping to unravel the secrets of Brine's mysterious past, the Onion and her crew sail into uncharted territory. Their aim, to find the legendary Western Island and its floating castle - where legend has it - there be dragons . . .