Thomas Jerome Newton is a space alien from the planet Anthea, which has experienced many nuclear wars and is home to people who are twice as intelligent as ourselves. He arrives to Earth, pretending to be a person, in Kentucky, with the goal of rescuing his own people from extinction. The extremely sophisticated Anthean technology that Newton patents allows him to amass a fortune. To assist the final 300 Antheans in their journey to Earth, he starts to construct a spaceship. Nathan Bryce, a chemistry professor in Iowa, is interested by some of the novel products that Newton's business introduces to the market and has a sneaking suspicion that Newton is an extraterrestrial. As Bryce and the FBI close in, Newton finds his own clarity and sense of purpose diminishing.