The Riddle Of Zorfendorf Castle (Turtleback School & Library Binding Edition) (Secrets of Droon)

FOR USE IN SCHOOLS AND LIBRARIES ONLY. Ko and his beasts are attacking Zorfendorf Castle, a magical fortress that's hiding the Fifth River, another passage to the Upper World. Ko will do anything to get to the Upper World. And Eric, Julie, Neal, and Keeah will do anything to stop him!