One summer day in Frog Creek, Pennsylvania, a mysterious tree house appeared in the woods.

Eight-year-old Jack and his seven-year-old sister, Annie, climbed into the tree house. They found it was filled with books.

Jack and Annie soon discovered that the tree house was magic. It could take them to the places in the books. All they had to do was to point to a picture and wish to go there.

Jack and Annie visited dinosaurs, knights, an Egyptian queen, pirates, ninjas, and the Amazon rain forest.

Along the way, they discovered that the tree house belonged to Morgan le Fay. Morgan was a magical librarian. She traveled through time and space, gathering books for King Arthur's library.

On their fifth adventure, in Night of the Ninjas, Jack and Annie found a little mouse in the tree house. Annie named their new friend "Peanut."

Jack and Annie also found a note from Morgan. The note told them that she was under a spell. To free her, Jack and Annie must find four special things.

They found the first thing in old Japan, and the second in the Amazon rain forest.

Now Jack and Annie and Peanut are about to set out in search of the third thing… in Sunset of the Sabertooth.