Join Jack and Annie on four time traveling adventures in books 9-12 of the #1 bestselling chapter book series! Morgan le Fay, the magical librarian of Camelot, challenges Jack and Annie to find the answers to four riddles. To do so, they must travel under the sea and to the Wild West, the African plains, and the frozen Arctic. It's a difficult and dangerous task, but if Jack and Annie succeed, they will become Master Librarians! Books in this set include: Dolphins at Daybreak (#9), Ghost Town at Sundown (#10), Lions at Lunchtime (#11), and Polar Bears Past Bedtime (#12). Did you know that there's a Magic Tree House book for every kid? Magic Tree House: Adventures with Jack and Annie, perfect for readers who are just beginning chapter books Merlin Missions: More challenging adventures for the experienced reader Super Edition: A longer and more dangerous adventure Fact Trackers: Nonfiction companions to your favorite Magic Tree House adventures