When Arthur's third-grade class goes hunting for fossils at Rainbow Rock State Park, Buster actually finds one. There's just one problem: he wants to keep it. Can Arthur persuade Buster to return the important discovery, or will it stay buried forever in the back of Buster's closet?

When Arthur's third-grade class goes hunting for fossils at Rainbow Rock State Park, Buster actually finds one. There's just one problem: he wants to keep it. Can Arthur persuade Buster to return the important discovery, or will it stay buried forever in the back of Buster's closet?

In chapter-book format for children who are ready to read on their own, this hilarious adventure will surely be a hit among Arthur fans.