Escape from the Planet of the Apes

Essential, and the best of the four sequels by a distance. It is also the one that makes the series into a loop: Cornelius and Zira escape the destruction of their world by travelling back to contemporary Los Angeles, and what happens to them there is what produces the future they came from.

The structure is the reason it works. For an hour it is a comedy. Two talking chimpanzees are debriefed by a government panel, become celebrities, appear on television, are taken shopping, and Zira gets drunk at a formal dinner and tells the truth about where she comes from. It is charming and very funny and it is the trap.

Then the film turns, completely and without warning, into something close to horror. Once the authorities understand what the future holds and who will cause it, the question becomes whether to prevent it, and the last twenty minutes are a hunt. There is a sequence in a disused ship that is as bleak as anything in 1970s American cinema, and the film does not soften the ending by a single frame.

Roddy McDowall and Kim Hunter are the reason the tonal swing holds, playing two scientists who are decent, married, frightened and frequently the only adults in the room. Made for very little money, mostly on location, and it is the entry that convinced people this series had more in it than a twist.