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 the times of dinosaurs, knights, pyramids, pirates, and ninjas. Along the way, they discovered that the tree house belongs to Morgan le Fay. Morgan is a magical librarian from the time of King Arthur. She travels through time and space, gathering books.

In their last adventure, Night of the Ninjas, Jack and Annie learned that Morgan was under a spell. To free her, Jack and Annie have to find four special things.

In old Japan, they found the first thing: a moonstone.

Now Jack and Annie are about to set out in search of the second thing… in Afternoon on the Amazon.