Zandor and Dorno rescue a man floating in the river who says he is from Gravite Island and tells them that a villain has taken over the island. The Herculoids go to investigate and are attacked by giant gravite creatures. The creatures are being created by Lotak, who wants the village because of its large deposits of gravite. Zok destroys the machine Lotak uses to make his creatures and Lotak is destroyed when his energy ray backfires.