The ending of Beneath the Planet of the Apes seemed to preclude the possibility of a third movie in the series, but with some creative thinking…
As the movie begins, the military is moving into position to handle the splashdown of an unknown spacecraft. The spacesuited aliens are helped from their floating craft – and, shock, it's Cornelius (Roddy McDowall) and Zira (Kim Hunter) from the previous movies.
Backstory: Simultaneous with the plot of Beneath the Planet of the Apes, chimpanzee genius Milo (Sal Mineo) repairs Taylor's submerged spacecraft, and launches into space with Cornelius and Zira as crew mates. From space, they witness the apparent destruction of future Earth.
Shocked by this knowledge, the simian astronauts decide not to reveal that they can speak. The authorities therefore send them to a zoo, where Milo is killed by a gorilla. They are then befriended by veterinarian Dr. Dixon (Bradford Dillman), and eventually the world learns that the simians are intelligent and can speak.
This leads to the light-hearted part of the movie, as Cornelius and Zira are exposed to human culture, Zira learns she is pregnant, the child is born and named Milo.
Meanwhile, trouble is brewing. The President (William Windom) doesn't want trouble, but his German-accented advisor, Dr. Otto Hasslein (Eric Braedon from Rat Patrol), believes the simans threaten the future of humanity.
This leads to the final part of the movie, as Hasslein goes rogue and tries to neutralize the simians. Also introduced is a circus owner, Armando (Ricardo Montalban). Cornelius and Zira, who as chimpanzees from the future see themselves as pacifists, have to make ethical choices.
After the second movie of the series, I was prepared not to like this one. But I did. Yes, the plot is a bit contrived in spots. Yes, you have to ignore the fact that Cornelius and Zira don't really look like real chimpanzees. It is funny at times, there is drama and action, and it zips right along.
The make-up novelty this time is that we get to see Zira injected with truth serum. It is the first time we've been shown a simian arm.
Note that this was Sal Mineo's final movie. Natalie Trundy has a small role as the veterinarian's assistant. She was the producer's wife, and appears in small roles in all the original sequels.
Can you wargame it? There's a pursuit through a derelict ship that could, with changes, turn into a skirmish scenario.
It was fun. Recommended. (And it sets up another sequel…)