From back cover: Major Perry Rhodan, commander of the spaceship STARDUST, found more than anyone had expected might exist on the moon -- for he became the first man to make contact with another sentient race!
The Arkonides had come from a distant star, and they possessed a knowledge of science and philosophy that dwarfed mankind's knowledge.
But these enormously powerful alien beings refused to cooperate with the people of Earth... unless Perry Rhodan could pass the most difficult test any human being had ever faced...