Thundarr, Princess Ariel, and Ookla escort a man who is carrying a magical black pearl that can defend against the two-faced wizard Gemini and his Groundlings (a race of mutated rat people). The man needs the pearl to protect the inhabitants of the village of "Manhat", which is actually the ruins of Manhattan.

An evil wizard and his minions seek a new body for him; they scheme to find ice people and force them to build a new body.