When Humphrey learns that school is ending, he was unsqueakably worried. What would he do once he lost his job as classroom pet?

It turns out that summer is wilder than Humphrey thought school could ever be. He sees new sights, makes new friends, and has FUN-FUN-FUN! But he also has to deal with new creatures, Og's mysterious disappearance, and the scary-sounding Howler!