Bumble the hamster, so called because of his big bum, belongs to Rosie. He knows it's his job to keep Rosie happy. He entertains her with Pocket Diving, Ear Tickling and Finger Balancing. But when he tries Hide and Seek, Rosie's parents panic and insist Bumble has to stay in his cage. Rosie still feeds him delicious things, but Bumble's getting bored - and fat!

Then mice arrive in the house. Rosie's parents are horrified, Rosie isn't happy - and Bumble is frantic. if things go on like this, he'll lose his job. He has to come up with a plan, and quickly...