Star Trek VI: The Undiscovered Country (1991)

The original crew's farewell is a political thriller. A Klingon moon explodes, leaving the Empire suddenly ready to make peace, and Kirk, who still blames the Klingons for his son's death, is sent to escort their chancellor to the talks. A conspiracy follows, with a murder mystery and a Klingon show trial along the way, so it plays more like a spy story than a space opera. Christopher Plummer is a delight as General Chang, a Klingon who quotes Shakespeare between volleys. Nicholas Meyer, who made The Wrath of Khan, directed. The politics need no Star Trek history to follow, though the goodbye at the end means more if you have seen a couple of the earlier films first.