I feel about this movie in much the same way Santiago felt about the fish in The Old Man and the Sea: I love it and respect it, but I must kill it. Undiscovered Country is an immensely clever, well thought out, thought provoking science fiction film, that unfortunately fails as a Star Trek film.
And it's also a really poorly done mystery story, but we'll talk about its failings as a Star Trek film first. And I have to warn you... I'm going to get really nitpicky.
Undiscovered Country is a not so thinly-veiled allegory about the Cold War and the fall of the USSR. The Federation are the United States, Klingons are the Soviets, The explosion of Praxis is Chernobyl, the dismantling of the Neutral Zone is the end of the Iron Curtain, etc. Even Klingon Chancellor Gorgon's name is ridiculously similar to Gorbachev's, as if we wouldn't have picked up on that without the hint. Unfortunately, as any long-time Trekkie could tell you, the comparisons simply don't work, because the Federation and Klingon empires were never really at war, Cold War or otherwise. But instead of broading the allegory and making it more than just a direct parallel of the Cold War, they changed the Star Trek universe itself to make the plot work.
So that's why we have Federation Officials asking moronic, unthinkable questions like, "Does that mean we're mothballing the fleet?" in regards to the news that the Klingons want peace. Or that the warriros in Starfleet are afraid they'll have no one else to fight. Have they never watched an episode of the original series, whose villains were Klingons maybe 10%, at most?
Bottom line, Starfleet exists for scientific exploration, not warefare. But you wouldn't know it from watching this film, where even the basic Starship procedures are changes from anything we've seen before to be more akin to American naval procedures. So nothing that takes place in the plot makes all that much sense, since there would never be much controversy over helping a dying race from reaching mass extinction.
That isn't to say things wouldn't be tense, nor that some people wouldn't be wary of forging a peace with a long-time enemy. Kirk's hatred of the Klingons is a staple of his character, and the arc he takes in the film to overcome those fears and emotions is heroic and brilliantly done. The film should've centered around the crews fears and emotions, not Starfleet's as a whole. It just doesn't work for me. And don't get me started on the notion that highranking Stafleet officers and Klingon warriors would ally themselves together into a conspiracy to end a peace process that would force Starfleet officers and Klingon warriors to become allies. Huh? Was that supposed to be ironic? Because it wasn't. It was just stupid.
And then we have a mystery story used as a device to move the plot along. Unfortunately, as mysteries go, it's not very well thought out. The knew the assassins used gravity boots on the Klingon ship, so Spock (not so logically) deduces that if they locate the boots, they will find the assassins. Why? Why can't they throw them away? Or leave them in the middle of the shuttlebay? What about the boots will actually lead them to the people who wore them? Or, here's a crazy idea, why didn't the assassins just put them back where they found them? Of course, this idea is proven to be illogical because when they find the boots, nothing is revealed. Duh.
And so the mystery continues, with very little clues given or deductions made that are the least bit logical. For a man who has written two Sherlock Holmes novels, Nick Meyer's ability to direct a good mystery is mysteriously limited. And then we have the not so shocking reveal that the traitor on the bridge is the one new addition to the bridge crew with an actual speaking part. And then the rest of the conspirators are revealed to be everybody else who was given lines earlier in the film. That's such bad writing.
And Chang has to be the most poorly thought out, annoying villain in Trek history.
Don't get me wrong, Khan was annoying too, and his entire character arc, and a good deal of his dialogue, was stolen from Captain Ahab. That never made sense to me. After his third or fourth reference to Moby Dick in regards to his need for vengence against Kirk, wouldn't somebody in his crew say something like, "Um... you know Ahab died in the end, right? I'm just saying."
But at least Khan's cartoonish behavior and overuse of literary quotes make sense in context. Chang just babbles Shakespeare at random. In every scene. For no reason. That finale where he keeps shouting different quotes over and over again is obnoxious.
But... the movie still works because it's a good story and because the actors are all so great. Among the films, this is the best use of Spock, who finally isn't either dead, a child, or suffering from amnesia. His illogical deductions throughout the mystery not withstanding, Nimoy is great in this movie and he has a lot to do. And, come on, Sulu is finally a captain! It's nice to see somebody other than Kirk and Spock getting a career boost.