A year has passed since Maisy and her friends returned from the dark lands of Zod, but peace never lasts long in the world of Eris. A reckless lie sets off a chaotic chain of events in Cambria. One of the Gale sisters is taken captive by a band of foreign rangers and whisked away across the Unicorn Sea. The Carin Six must embark on a perilous journey to save her before the mysterious queen of Cyrus discovers what she has been searching for. Powerful forces have begun to move across their world; an ancient evil is stirring. Will they reach her in time, or will the monsters of the wild Unicorn Sea claim them all?