More adventures with saboteurs intent on disrupting giant society, as the group becomes embroiled with the mysterious Dr. North, who is planning a major terrorist outrage.

The Earthlings are sneaking into a circus to steal explosives when an escaped gorilla captures Valerie. With the aid of an elderly puppeteer, Goalby, Valerie is rescued. Betty then wanders into a bear trap, and Goalby frees her but injures his right hand. Betty and Fitzhugh decide to help Goalby win his audition by becoming 'puppets'.