This is a classic science fiction novel by John W. Campbell Jr., author, and editor of Astounding Science Fiction and Analog Science Fiction and Fact. This story tells the tale of the Miran people and their exodus from the system of their unpredictable star Mira. They travel at the speed of light toward a new star, Sol, where they plan to take over the solar system and settle. This is Earth's solar system and we have no way of defending ourselves against the invaders - no way that is, until Buck Kendall discovers the Ultimate Weapon and our only chance of survival. This work is part of our Vintage Sci-Fi Classics Series, a series in which we are republishing some of the best stories in the genre by some of its most acclaimed authors, such as Isaac Asimov, Marion Zimmer Bradley, and Robert Sheckley. Each publication is complete with a short introduction to the history of science fiction.