Twinsen has been the hero of the planet Twinsun since he vanquished the evil dictator Dr. FunFrock in Relentless. Trouble begins with the arrival of unidentified space ships piloted by strange beings called Esmers. Twinsen, now a graduate magician, is kidnapped by the Esmers and taken to the planet Zeelich. He learns of their plot to kidnap the children of Twinsun, but is too late to stop it. The Esmers, under the spell of their mysterious god, the Dark Monk, have also built powerful jet engines to ram the Emerald Moon into Twinsun and destroy it. Twinsen must battle the aliens and their mysterious god, the Dark Monk, and save his planet and family.