As the performers in Sir Sidney's circus discover that friendship and teamwork are more important than winning a trophy for The Greatest Star on Earth, circus mice Bert and Gert write a book on how to be kind for rotten ringmaster-in-training Barnabas Brambles to read.

Two mice and a crow, who travel with a circus, cleaning up the spilled popcorn after every performance, come to the rescue when a greedy con artist takes over the management of the circus.