A trio of astronauts are thrusted forward in time and space. They find themselves fugitives after crash landing on the Planet of the Apes. Can they survive a relentless pursuit?

General Urko's gorilla army launches an attack on the humanoids' caves and Jeff is nearly killed as a result. Jeff is able to hide with Nova in the hopes of evading capture by Urko's troops.

Urko and his gorilla army set out into the desert in search of the secret entrance to the Under-dwellers caverns. Will they succeed or can they be stopped before it's too late?