Cross Island is a mysterious uncharted island in a little-known sea. Here a task force of robots work in great secrecy extracting valuable stores of Uranium. One day, the diabolic scientist, Dr. I. M. Sinister, returns in disguise to Cross Island after his daring escape from prison. His plan is to take over the island with the help of Bobo, a mischievous little robot created by Dr. Sinister just before his imprisonment. The evil doctor endows Bobo with super-powers-powers to enable Bobo to cope With any other robot on the island-even Astro Boy. Astro Boy arrives, finds the criminals at work, and engages Bobo in a spectacular struggle. Not even Bobo’s super-powers, however, can defeat Astro Boy. Bobo and Dr. Sinister, shown the folly of their ways, reform and Astro Boy saves the day!