The trio find a long-buried human science institute, but the projector revealing the vault of hidden knowledge is out of power. While Pete and Galen collect parts to make a battery, Urko and Zaius capture Alan and try to obtain the institute's location from him.

When Alan is badly wounded by an ape bullet, Galen must convince his former girlfriend--a chimpanzee surgeon--to operate on his friend using a forbidden human medical textbook.