Paul Dehn wrote every one of the original Apes films, but after providing the story idea, an illness made him leave the project. John William and Joyce Hooper Corrington (The Omega Man) came in to write the movie, despite never seeing any of the previous films.

Dehn was unavailable for the initial rewrites, but was hired to come in and do one more pass. He was only given a story credit, despite an appeal to the Writer’s Guild of America for shared credit on the screenplay, despite rewriting 90% of the dialogue and adding a new ending.

While the original script ended on a playground with ape and human children fighting, now it would close on a statue of Caesar with a tear falling from its eye. Joyce Corrington called ythe new ending stupid and claimed that “It turned our stomachs when we saw it.”

The budget for this one was $1.7 million, a figure that director J. Lee Thompson felt wasn’t enough. He also wasn’t happy with the script, regretting that Dehn wasn’t on board throughout the entire process.

In the future — 2670 A.D. — a Lawgiver (John Huston!) explains that Caesar led the apes after mankind wiped itself out in a nuclear war. The ape leader, along with his wife Lisa (Natalie Trundy, reprising her role) and son Cornelius, are attempting to create a new society where human and ape can live together. Opposing this is the gorilla Aldo (Claude Atkins!) who wants to imprison the humans and make them do slave labor.

After an incident between Aldo and a teacher, Caesar doubts his leadership and wishes that his parents could have taught him more. MacDonald, Caesar’s human assistant and the younger brother of the similarly named character from the last film — played by Austin Stoker —  knows that there is archived footage of them in the Forbidden City. So the two are joined by Virgil (Paul Williams, who of course had to end up in this series) on a quest to see this video.

However, there are mutants living within the city, led by Governor Kolp (Severn Darden), the man who once captured Caesar. Soon, Kolp declares war on Ape City despite his assistant Mendez’s trying to calm him down. Later in the film, Mendez is asked to set off an atomic bomb if the humans don’t win their battle against the apes. Mendez refuses, which is the start of the mutant cult that we saw in the Beneath the Planet of the Apes.

Speaking of people named Mendez, this is the film that inspired Tony Mendez to create the operation “Argo” during the Iran hostage crisis. The film Argo dramatizes this tale, as Mendez traveled to Iran in disguise as a film producer and had the hostages disguised as a film crew in order to flee the country.  There’s a clip of this movie within that movie, showing the moment when Caesar, MacDonald and Virgil arrive in the Forbidden City.

Aldo plans a coup against Caesar and when Cornelius overhears, Aldo hacks off the tree branch he’s on, critically wounding the young ape. Kolp attacks, but the tide soon turns and he runs, leading Aldo to follow him and ruthlessly slaughter all of the retreating humans.

Aldo returns to try and take Caesar’s power, Virgil reveals that the milittary leader has broken the most sacred law – “Ape shall never kill ape.” Aldo falls to his death and he attempts to treat humans as equals.

In the future, the Lawgiver tells a mixed audience of young humans and apes, that their society still waits for a day when their world will no longer need weapons, as a closeup of a statue of Caesar cries a single tear.

Lew Ayres — who played Dr. Kildare in nine movies — also shows up as the orangutan Mandemus, the keeper of the weapons. The actor was a well-known pacifist, so there’s some resonance in how much the character believe that he must protect the weapons from the warlike gorillas. He believes that the guns are only for defense, not offense.

This would be the last theatrical Apes film for awhile, as producer Arthur P. Jacobs died a few days after the film’s release. As to the future of the Apes, stay tuned as we will soon get to the TV series that followed.