While exploring their grandfather's farm, Max and Hannah discover hundreds of round rocks piled up in the corner of a field. The children seek out Grandpa to learn how the rocks got there and why the rocks are round. The Mystery of the Round Rocks explores part of the geological history of South Dakota. The story begins with huge mountains and vast glaciers that form rivers and thousands of small round rocks. Along the way, watch out for saber-toothed tigers, woolly mammoths, and short-faced bears.
Max and Hannah's discovery that their grandfather has kept a journal since he was a young boy impresses them, but Grandpa has a different kind of journal in mind when he whisks them off to the Black Hills for a mystery-solving trip. When they arrive, the children and Grandpas set off on a hike to find a ponderosa pine nearly eight hundred years old. Along the way, Max gets lost and sits down to rest against a huge pine tree. A mysterious voice speaks to Max, and soon he discovers the secrets wrapped up in the life of Rosa the ponderosa. When Hannah and Grandpa eventually find Max, he has all the answers to what is inside that ancient journal.
