Cubbi becomes obsessed with flying after hearing a story of the mythical Aerials. He builds a gummiberry-juice-powered jet pack and has Artie instruct him, and finds their floating island. But the Aerials aren't winged like legends say but use machines...and they have another secret: they're old enemies subdued by the Ancient Gummies and plan to capture the Gummies and enslave them to power their aircraft like Cubbi did his "wings". Artie overhears but is captured before he can warn Cubbi, who returns convinced the Aerials are friends. While he is shut up in his roof after getting home, Gummi Glen is attacked and the other six captured, forcing him to try to find a way out and free them.
—brainybrailler@comcast.net