Sitting alone at the beach one day, watching wave after wave break on the lonely sand, Astro Boy spotted a mysterious bottle being washed ashore. The bottle proved to contain a note calling for help and rescue from a dreaded but unknown, uncharted island called Sea Serpent Isle. The note was signed ”Princess Papaya Petal.” Doctor Elefun knew nothing of Sea Serpent Isle other than that many ocean liners in recent days had disappeared after reporting sightings of giant sea serpents. And these disappearances always occurred in the same region, although there were no islands in that particular part of the ocean. Astro Boy’s investigations over and under the water revealed that there was indeed an island-not a natural one, but a man-made base that, like a submarine, could appear or disappear at will. Giant tentacles shaped like sea-serpents attacked ships at sea: pirated the ship’s cargo, then forced the passengers to work at hard labor upon the “island.” Astro Boy himself was captured. Taken to the base “hospital,” he met Princess Papaya Petal…and devised a plan for escape. Prisoners were sent floating to safety within giant laboratory bottles while Astro Boy himself set out to stop the men and machines behind the threat of ”Sea Serpent Isle.”