Continuing the New York Times bestselling series, Jessica Day George brings readers on another magical adventure in Castle Glower. Life for Princess Celie and her family is finally back to normal now that the Eye of the Castle has been restored and the Castle is whole. With more magical griffins to care for, Celie, Lilah, and Rolf have their hands full. But when the evil Wizard Arkwright hides himself in the Castle's secret passageways and threatens to wield his magic against the Castle and the king, Celie and her family must stop him. Heading underground to the labyrinth of secret tunnels beneath the castle walls is the only way to defeat Arkwright once and for all, but will Celie be brave enough to face such danger? Readers will delight in the newest installment of this bestselling and beloved series, as Celie and her siblings work together to protect their Castle.