After saving a old man named Tyron from the rat-like Groundlings, Thundarr, Ariel and Ookla learns that the Groundlings are in search of The Black Pearl, which the evil wizard Gemini fears it's power. Thundarr, Ariel and Ookla agrees to deliver the Black Pearl to the village of Manhat (the ruins of Manhattan). But Ariel is captured and taken to Gemini's tower and Gemini demands that Thundarr and Ookla gives him the Black Pearl or Ariel will die.