Fergus, the pet mouse in Miss Maxwell's classroom, stows away in a backpack on a field trip to the museum. He makes a new friend, Zeke, another mouse, who shows Fergus many interesting exhibits, but now he wonders how to get back to school.

Class pets Fergus and Zeke, who like to do everything the students do, go outside for Field Day only to find none of the sports are suitable for mice, so they come up with their own events and then discover they have been locked out of the classroom.