While on a mission, three astronauts in their spaceship get caught in a time vortex. They return to Earth in the year 3979 A.D. and discover that intelligent apes are now the highest form of life.
"The Simian Senate is holding a top-secret session debating the possibility of intelligent humans after one of Urko's soldiers returns, delirious from the Forbidden Zone."
"Bill and Jeff discuss the best means of eluding Urko's troops when Judy insists that the laser previously rescued from the ship be used as a source of escape."
"Bill, Jeff and Judy head for the human settlement across the plain between the mountain ranges when they spy human shapes far below. A WWII Curtiss P-40 appears in the sky..."
"Bill, Jeff and Judy begin building rafts to help the human tribes reach New Valley. As always, Urko is in pursuit. I wonder if he gets paid overtime..."
"Urko has been relieved of his duties for three months because of his recent negligence involving his leadership and the failed attempts at capturing Blue Eyes and the rest of the humans."