A spaceship lands on earth, a man disembarks, sleeps with a woman, and then he leaves on his spaceship. The woman becomes pregnant. The son she gives birth to is the most intelligent person alive. Hoping to find more people as intelligent as he is, he searches the galaxy for his father, having adventures along the way. At one point he solves a mathematical puzzle created by a genius of a prior era. Nobody has been able to solve the puzzle, but he does, and he discovers that it is a joke. Eventually he finds his father, who turns out to be an ordinary man, not part of a race of extraordinarily intelligent people.