Star Trek VI: The Undiscovered Country

Essential, and the best possible ending for this crew. Nicholas Meyer, who had directed Wrath of Khan, returned to close the series, and he made the most politically pointed film in the franchise.

The allegory is not subtle and is better for it. An environmental catastrophe forces the Klingon Empire to sue for peace, the Federation has to decide whether to help an enemy it has spent seventy years hating, and Kirk is openly, uncomfortably against it because a Klingon killed his son. It was released weeks before the Soviet Union dissolved and it is a film about old soldiers discovering that the thing which gave their lives shape is being negotiated away without them.

Making the hero the bigot is a real risk and the film takes it. Kirk's arc is not learning that Klingons are good; it is admitting that he has been holding a prejudice he was comfortable in, and the dinner scene where both delegations are drinking and nobody is quite saying what they mean is the best-written sequence in any of the films.

It is also a murder mystery with a conspiracy, a prison break and Christopher Plummer quoting Shakespeare through an eyepatch bolted to his skull. The final shot and the signatures over it are the correct full stop. Watch it last of the six.