Nuclear testing has resulted in the abrupt evolution of the Fumoon, a tiny but highly intelligent humanoid race on a small island, who are detected by Dr. Yamadano. Except for a few witnesses including the detective Shinsaku Ban, and the young men Rock and Kenichi and Kenichi’s sister Pichi (Pinoko), no one believes him. The Fumoon are kidnapping animals from around the world to bring with them as they use their space ships to evacuate the earth, because they know Earth is shortly to be destroyed by an enveloping cloud of black gas created by a stellar explosion. The Fumoon intend to abandon mankind, but one Fumoon, Rokoko, who becomes good friends with Kenichi, tries to help Dr. Yamadano and the others to develop a space ship to allow a few humans to escape, with the help of Dr. Ochanomizu and Dr. Frankenstein.