A real estate broker named Jonas T Smith, taking on the identity of Thor Kol, a ruler of Krypton from long ago, has started a Krypton-themed island where people can come and buy property. The island is called Krypton Island.
Clark Kent takes the Flying Newsroom helicopter to investigate. When he learns the nature of the island, that it is a tribute to his home planet, he soon agrees to appear as Superman in publicity shows at the island. However, unknown to him, Jonas Smith is using him in a get-rich-quick scheme. When Superman creates diamonds out of coals to be displayed, Smith secretly switches them out for fake diamonds.
However, Superman soon catches on to the ruse, and nabs the crook. He allows Krypton Island to continue under new management, however. The island is renamed Kryptonopolis.