Brun leads the humans of his village. The leaders pass their secret from father to son, the secret of how to make poison gas. He follows the old tradition of handing over five humans a month to the local ape garrison as slaves. The fugitives find this practice, disguised as a religious ceremony, horrific. The slaves are preferably captured from other human settlements, but if not, they must select some of their own humans. Ultimately, the astronauts discover that Brun is secretly plotting to create enough gas-bombs to wipe out the apes. The astronauts and Galen also find this immoral. When they accidentally set fire to his temple, Brun runs back in to try to rescue the bombs, but is killed in the explosion.