In an urban biological research facility, Ulysse recognizes conditioning methods being used on captured humans. He is mated with Nova. Curious chimpanzee researcher Zira takes an interest in his geometric drawings and his ability to speak a few simian words. With help from Zira's fiancé, Cornélius, Ulysse makes a speech in front of several thousand apes. He is granted freedom and is given tailored clothing. Antelle reverts to primitive humanity in the zoo and is moved to the laboratory for safety, where he is mated to a young female.