Steve Holbrook, with his defense reserve squadron, is called upon to resist the incursion of an unknown star cruiser. The defenders fail to prevent the cruiser from destroying their world, but manage to survive. Who destroyed the planet and the pioneers who lived there? How was it done? Why would anyone destroy an out-of-the-way agricultural planet in such a destructive display of power? To track down and apprehend the one responsible, Steve will rely on friends old and new, follow a trail of clues, endure an assassination attempt, use powerful new technologies, and discover something alien...