As a science fiction editor, Keith rather despised space opera, but now finds himself living in a "Mad Universe" where the most cliché aspects of that subgenre are an actual, daily reality. At first inclined to regard all this as a bit far-fetched, he is reprimanded by this world's version of his beloved Betty: "Do you think the danger of all humanity being exterminated is a matter for joke?" In order to have any hope of getting back to his own world, he has to get in touch with the impossibly 'larger than life' hero who leads Humanity's struggle against the Arcturian menace, helped by an "artificial brain" sidekick Mekky.