Some spoilers here *************************************************************
Star Trek VI: The Undiscovered Country" is the final film with the entire original cast. This is also one of the best of the series because we see the Enterprise crew, past their prime, save the universe one more time.
As the film opens, we are witness to an ecological disaster. As the starship Excelsior, now under the command of Capt. Sulu (George Takei)is on a survey, they witness the aftermath of the explosion of the Klingon moon called Praxis. Even though Sulu is ready to offer assistance, The Klingons want no help from them.
Later, the Enterprise crew is called into a top secret meeting and is apprised of the situation,which is dire (Think Chernoble). Because of the devastation (Which will destroy their ozone within 50 years), the Klingons offer to extend an olive branch with the Federation. In other words, The Klingons and The Federation want a peace treaty.
Considering that the Klingon Empire and the Federation have been at each others throats for ages, this doesn't sit well with the parties involved, especially Captain Kirk (William Shatner), who wants nothing to do with the process considering that it was the Klingons who had killed his son (See "Star Trek III: The Search For Spock"). In fact, when Mr. Spock (Leonard Nimoy), who has been working with the Klingons for the treaty, tells them that they are dying, Kirk viciously says "Let them die!" Ouch. However, he has to follow orders.
Soon the crew of the Enterprise meets with Chancellor Gorkon (David Warner), his officer General Chang (Christopher Plummer) and his daughter Azetbur (Rosanna DeSoto). During a dinner in which pretty much everyone is intoxicated with Romulan Ale, there is some negativity among both sides, clearly indicating that the road to peace is going to be a bumpy one.
And it is.
Later, the Klingon ship is fired upon, seemingly by The Enterprise, and the Chancellor is assassinated, despite the attempts of Kirk and McCoy (DeForest Kelley) to save him. Both Kirk and McCoy are arrested and put on trial. Found guilty, both are sentenced to the ice planet known as Rura Penthe. How bad is it? Judging from Uhura's (Nichelle Nichols) and Scotty's(James Doohan)reaction, it would have been better for Kirk and McCoy to have been executed on the spot.
Spock knows that a conspiracy is present. And so, while he is trying to find out the facts, Kirk and McCoy try to stay alive on the penal planet.
With time running out before the peace conference starts, the crew of the Enterprise must not also save Kirk and McCoy, but to race to the site of the conference to stop another assassination from taking place, which will destroy any chance of peace. This proves even more difficult when they discover that there is a Klingon Bird of Prey that can fire when cloaked. And that those involved in the conspiracy work on both sides of the coin.
What is interesting about the film is that it mirrors the general feelings between the U.S. and the former Soviet Union. Once considered enemies, each side works together for peace, even if both sides are skeptical. We also see the flaws of the crew of the Enterprise: everyone is prejudiced. Chekov (Walter Koenig), during dinner, mentions "unalienable human rights," and is chastised by Azetbur for his "racist" comments. Even Mr. Spock is prejudiced: he's so blinded by the accomplishments of his Vulcan protégé Valeris (Kim Catrall), that he doesn't see how much of a threat she is (He admits this to Kirk later on) until it is almost too late.
It is nice to see the crew back in action one last time, and you can't help but get a bit misty eyed (Gene Roddenberry, the creator of Star Trek died before it's release, and this film is dedicated to him). A nice way to end the series, but it's hard to say goodbye.