 The book then proceeds to go back forty-four years, tracing Wireman's career to its very beginnings, and answering the questions which would elude all later observers.The story takes place in the 25th century, four hundred years after humans have begun colonizing other planets, and a generation after the home planet, Earth, has been conquered by the Invaders.The Invaders (whose name for themselves in never given) in this case are humanoid, very similar to Earth humans.