After ten years of solitary contemplation, the prophet Zarathustra descends from his mountain cave to deliver a message to the people below. In a town called The Pied Cow, he tells everyone about the Superman, a higher being who is free of all human prejudices, and unbound by societal constraints and the false concepts of good and evil. Zarathustra informs the people that they can achieve this state if they reject the teachings of the past, including among other things, the notion of an afterlife, and embrace instead a new set of values based on the truth that humans are of the earth and the body—that they are of this present life—and nothing else.

With the exception of a fallen tightrope walker who soon dies from his injuries, the townspeople do not seem to care about what Zarathustra has to say. The prophet soon realizes that the great majority of people are not ready to wage the inner battle required become the Superman, so he sets off on a quest for the select few who are strong enough to master themselves and overcome all that they have been previously taught.

The protagonist Zarathustra is actually the ancient Persian prophet known to the Greeks as Zoroaster, placed here in a fictional setting. Friedrich Nietzsche chose him to be the central figure of this epic work because he believed that Zoroaster, as the first philosopher to declare that the struggle between good and evil is the defining characteristic of the universe, should also be the first to recognize the error of this concept and move beyond it.