When she finds the key to a secret passageway leading out of the walled city of Bridewell, twelve-year-old Alexa realizes her lifelong wish to explore the mysterious forests and mountains that lie beyond the wall.

Alexa reveals the origin of the Land of Elyon while defending it against the evil Abaddon and his sinister forces, with not only the last Jocasta at stake but also the nature of the land itself.

Twelve-year-old Alexa and her companions unwittingly lead Abaddon, now in the form of an enormous, horrible sea monster, to the secret community known as the Five Stone Pillars when they go to bring the people living there home.