Unlocked cage door is still a mystery; a cloud of suspicion hangs over one student.
The good news: The students of Room 26 have built a model community and named it Humphreyville in honor of their beloved classroom pet.
The bad news: When Humphrey escapes from his cage, he sets off a chain of events that has serious consequences for one of his favorite friends, Golden Miranda. In order to make things right for her, he'll have to give up his treasured freedom.
Meanwhile, Humphrey has to help Sit-Still-Seth learn to settle down, and come to the aid of Don't-Complain-Mandy-Payne, even though her family is behind a battle to get Humphrey banned from Room 26 forever!
It's up to Humphrey to solve the problems of Room 26, but only if he survives the perilous train ride of a lifetime, thanks to Pay-Attention-Art.
The question remains: how much TROUBLE can one little hamster get into?