When Planet of the Apes (1968) was a giant hit, the studio rushed this sequel into production.
It starts where the last movie left off, recapping the final scenes as astronaut Taylor (Charlton Heston) and primitive human Nova (Linda Harrison) ride off into the Forbidden Zone.
However, Taylor disappears into some kind of psychic illusion (not to reappear until the movie conclusion), and Nova is left to wander the wastes until she chances on another crashlanded astronaut – Brent (James Franciscus), sent to rescue Taylor's crew.
This eventually leads back to Ape City, where we meet again with Cornelius (now played by David Watson), Zira and Dr. Zaius from the previous film. We learn that gorilla general Ursus (James Gregory) plans to lead a gorilla army into the Forbidden Zone to investigate strange phenomenon.
This sets everything up for a grand three-way confrontation in the Forbidden Zone, secrets are revealed, creepy mutants are exposed, and there's another dramatic ending.
Everything about this sequel is a step down from the original. It feels more like a TV movie or a bad Star Trek episode. I like James Franciscus as an actor, but he is given little to do but rush from place to place. Linda Harrison is sexier than ever, but her character is just a sidekick. James Gregory makes a nice gorilla, though, and Maurice Evans remains villainous.
One novelty this time is to see apes in a steam bath, which was an advance for the make-up team. It's also impressive to see so many gorilla soldiers.
One inconsistency is that the gorillas in the first movie were the lowest rung of simian society, so it is jarring to see General Ursus so much in power in the sequel.
The problems of this sequel are numerous. There is too much rather boring action, the idea of New York City being 'beneath' the ground is ridiculous (covered by flowing liquid rock?), the mutants are wimpy, the big surprise at the ending is shocking but also laughable, and the ending is a downer.
Watch it only if you need to see every movie in the series, or if you want to laugh at it. Not recommended.