Sunni is kidnapped by a flock of ugly bird-like creatures known as Carpies, whose king wants her for a song bird. The Gummis (Gruffi, Zummi, and Cubbi) must use their new flying machine to get to the top of the mountain and rescue her, all whiledealing with Zummi's acrophobia and Gruffi's insistence that "Gummis were not meant to fly".