Arthur's wrong guess about the identity of the secret admirer sending him valentine messages leads to teasing by the other children, but clues in additional messages allow him to get his due.
When Arthur's third-grade class goes hunting for fossils at Rainbow Rock State Park, his friend Buster actually finds one, and instead of turning it in Buster decides to take it home--but he soon regrets his decision.
Arthur worries that he won't be able to play little league baseball as well as all his friends and faces lots of teasing until someone discovers teamwork.
Although Arthur and Francine aren't speaking to each other, they must find a way to set aside their differences when they are locked in the library after it closes.