This fourth in the simian series carries on twenty years after the depressing conclusion of the last instalment. Humans have just seen a virus cause the extinction of their ideal pets; subservient dogs and cats. Now apes are being mass trained (tortured) to substitute for the lost pets. But soon the human's tire of the novelty of their new furry pets and find far better use for them as slaves.

Meanwhile, the baby chimp born to Zera and Cornelius has grown into Milo under the protection of Armando, ( Montalban) the benign circus keeper, but Milo must hide from the world the fact that he can articulate and form intelligent thought…..in case he is savagely put down like his parents had been years ago. The country is ruled with an iron fist by a posse of Nazi wannabe's who control all aspects of life with an all seeing "big brother" like government that tolerates no nonsense/opposition. The government suspects that Milo is alive and that as long as he remains as such, constitutes a threat to the superior race as there is a chance that he could subsequently shape an ape dissident movement. Thus all efforts are being made to discover Milo and eliminate him and the potential threat.

Montalban does his best to try to protect the chimp but ultimately the apes' plight is best understood by an American of African origin working for the government whose own people have been through the same humiliation and degradation (that the apes are experiencing) with their long and painful struggle against slavery. He is part of the core, yet always an outsider. Milo (now called Caesar) hides out among the downtrodden slave population and begins to organize them into a seething revolutionary mass. Weeks later, every able bodied ape is armed and ready to lay down their lives for the cause of freedom from mankind's oppression.

One fateful night, the apes turn on their tormentors and though they are met with brutal firepower, their resolve remains unshaken. Wave after wave of apes rise up in defiance and the humans are confronted with an enraged mass demanding justice for all the horrors that have been perpetrated on them. The question is now that the shoe is momentarily on the other foot will the apes be able to rise above their feelings of hatred and revenge and be able to build a future where both man and ape can live in respect of one another or will we revert to the situation where one side is subservient and tormented and the other consumed with their own power and glory?

It's yet another of the Ape films desperately trying to inject some fresh morality to its tale, some justification for being a third sequel with nowhere to go! It's a tale of humans being nasty, intransigent and insensitive to their fellow beings…..and trying to explain how one form of extremism will almost certainly lead to another equally brutal regime in reaction. The message is certainly universal and very noble indeed, yet it is dressed up in a film that is dull, lacks tension and focus and is as soft as a subtle as a sledgehammer with its moralizing.

Roddy McDowall tries hard to elevate the movie above the utterly average, but even his commendable efforts fail to rise above a very drab, uninspired script. There is some fangled, trendy early 70's pseudo-socialist notions hidden away somewhere between the turgid lines, but who cares when it is done with such little imagination!
Quite amazing that the producers of the series had it in them to churn out yet another sequel and the story is set to continue as this one comes to an end. Yawn!