Fergus loves being the class pet in Miss Maxwell's classroom. He does everything the students do, until the teacher plans a field trip to the museum -- without Fergus! He doesn't want to miss the fun, so he stows away in a backpack and sets off for an adventure. When he arrives at the museum, Fergus finds it a little overwhelming -- huge and full of exciting things to see. Luckily, he meets a new friend, Zeke, who knows the ropes, and together they explore everything from moon rocks to butterflies to a giant dinosaur skeleton ("A playground!" says Zeke). But when the time comes for the bus to leave, Fergus is worried that he'll be left behind. Will he make it back to school to take his place as class pet once more?