It is some years after the fall of humanity, and the world has been bombed into a more primitive age. Caesar (Roddy McDowall), who led the Apes in their uprising against Mankind, now lives in a settlement where Gorillas, Chimpanzees and Orang-Utans live in relative peace with humans. However, in a nearby city, mutated humans live amongst the devastation, and in this city is a library where Caesar hopes to find tapes of his parents - leading to a dangerous confrontation...
Producer Arthur P. Jacobs was scraping the bottom of the barrel for this, the final installment of the Apes saga (as it was advertised). Written by John William Corrington and Joyce Hooper Corrington from a story by Paul Dehn, it attempts to bring the story full circle, but really doesn't add much to anything that the previous film, Conquest of the Planet of the Apes, had already made clear in its grand finale. The film actually comes close to an unwitting self-parody in its re-heating of the series' main features.
With a flimsy starting point, Caesar wanting to see the archive footage, the action is set up for major hostilities by the end. Before we get to that, we are shown that all is not right in the Ape/human settlement. Where the Apes were the underdogs before, humans are now second class citizens with the Apes as benign rulers. All except for the Gorillas, led by Aldo (Claude Akins), who remain aggressive and suspicious of all contact with humans - so when the mutant men are on the warpath, it's the only excuse they need to instigate a coup.
The philosophical angle is present, but now it comes from a more uninspired angle. We can tell the Chimps and Orang-Utans are wise, because they speak in aphorisms. Now the race relations theme has normal humans as the oppressed (the mutants bring out the worst in eveybody) when the Gorillas have them rounded up (and humans are never allowed to say "no" to Apes, because it reminds them of their years of oppression), but this doesn't have the potency of the preceding installments.
Anyway, despite the sorrowful tone about conflict, everything leads up to a big fight - this isn't called Picnic on the Planet of the Apes, after all. But neither does it come across as a battle for a whole planet either, more of a skirmish between neighbours. If there is a message, then it's that it matters little what you race or background is, there will always be a propensity for violence or even war. The last shot is of the statue of the Lawgiver shedding a tear - sorrow for the breakdown of society, or sorrow that general interest in the Apes franchise had run out? Music by Leonard Rosenman.