Reading level: Ages 9-12
Hardcover: 192 pages
Publisher: Scholastic Inc. (June 2, 2009)
Language: English
ISBN-10: 0545060443
ISBN-13: 978-0545060448

A Clue found in Book 3 sends Amy and Dan jetting off to find out just what's behind the fierce rivalry between the Tomas and Ekaterina branches of the Cahill family. Was a Clue stolen from the Tomas branch? Where is it now? And most important, can Amy and Dan get their hands on it before their rivals do?

It's a wild race that will take Amy and Dan deep into the bowels of the earth . . . and right into the hands of the enemy.