Startling Stories The series was originally set in 1990; as the series progressed, Hamilton quickly stopped using exact dates (except as "in the past" as in the voyages of the astronauts who first landed on most of the other planets of the Solar System), sticking with a series continuity. In later stories, if the date was asked or revealed, it was done so discreetly.

The series begins when scientist Roger Newton, his wife Elaine, and his brilliant fellow scientist Simon Wright leave planet Earth to do research in an isolated laboratory on the moon. Simon's body is old and diseased and Roger enables him to continue doing research by transplanting his healthy brain into an artificial floating case. Working together, the two scientists create an intelligent robot called Grag, and an android with shape-shifting abilities called Otho. The criminal scientist Victor Corvo (originally: Victor Kaslan^[2]) arrives on the moon and murders the Newtons.

The deaths of the Newtons leave their son, Curtis, to be raised by the unlikely trio of Otho, Grag, and Simon Wright. Under their tutelage, Curtis grows up to be a brilliant scientist and as strong and fast as any champion athlete. He also grows up with a strong sense of responsibility and hopes to use his scientific skills to help people. In the first adventure, he offers his services to the President of the System. The publicity-shy Curtis takes the alias Captain Future. Simon, Otho and Grag are referred to as the Futuremen in subsequent stories.

Other recurring characters in the series are the old space marshal Ezra Gurney, the beautiful Planet Patrol agent Joan Randall (who provides a love interest for Curtis) and James Carthew, President of the Solar System whose office is in New York City. A young boy called Ken Scott was exclusive to the anime.

Captain Future faces many enemies in his career but his archenemy is Ull Quorn, who is the only recurring villain in the series and appears in four different stories. He is part Martian – therefore called the Magician of Mars – but also the son of Victor Kaslan, who murdered the Newtons. Quorn is a scientist whose abilities rival those of Captain Future.