"Twelve-year-old Brine Seaborne and her friend Peter find themselves in an adventure with pirates, invisible bears, and a seriously evil magician"-- Provided by publisher.

Found alone in a rowboat as a child, clutching a shard of the rare starshell needed for spell-casting, Brine Seaborne has spent the past years keeping house for an irritable magician and his obnoxious apprentice, Peter. When Brine and Peter blunder into the path of the legendary pirate ship the Onion, they're soon up to their necks in the pirates' quest to find Magical North, a place so shrouded in secrets and myth that most people don't even think it exists. Pirates, invisible bears and a seriously evil magician... and everyone on the ship might be eaten by sea monsters. It could really go either way.