Who stole the wizard of oz

Becky is in big trouble. The Checkertown librarian has accused her of stealing a rare children's book! Now she's got to clear her name by tracking down the real culprit with the help of her twin brother, Toby. Together they investigate a string of bizarre crimes about town-including the disappearance of four more children's books. The twins soon find clues in the stories themselves that point the way to a secert treasure! But can they figure out the treasure map before the thief doea?.