Three astronauts crash-land on a strange planet where talking, intelligent apes rule over primitive humans. The explorers must survive in this upside-down world where humans are treated like animals and apes are the civilized masters. The story follows journalist Ulysse Mérou as he tries to prove his intelligence to the ape society while uncovering the planet's shocking secret. This thrilling adventure makes readers question what truly makes someone civilized and explores the dangers of prejudice.