Star Trek VI: The Undiscovered Country (1991, 113 minutes, PG)

Writing Team
Gene Roddenberry, Leonard Nimoy, Lawrence Konner, Mark Rosenthal (Story)
Nicholas Meyer, Denny Martin Flinn (Screenplay)

Main Cast
William Shatner as Captain James T. Kirk
Leonard Nimoy as Captain Spock
DeForest Kelley as Dr. Leonard McCoy
James Doohan as Captain Montgomery Scott
Walter Koenig as Commander Pavel Chekov
Nichelle Nichols as Commander Nyota Uhura
George Takei as Captain Hikaru Sulu
Kim Cattrall as Lieutenant Valeris
Mark Lenard as Ambassador Sarek
Grace Lee Whitney as Commander Janice Rand
Brock Peters as Admiral Cartwright
Leon Russom as William Smillie
Kurtwood Smith as the Federation President
Christopher Plummer as General Chang
and Rosanna DeSoto as Azetbur

An explosion on the Klingon moon Praxis has left the Klingon homeworld in dire straits. Due to high military spending, the Klingon government is unable to deal with the ecological disaster that will wipe out all life on the planet in half a century. With no alternative in sight, the Klingons go to the Federation for help, ending decades of war. However, it seems that the Federation flagship attacked the Klingon Chancellor's ship, after which two Starfleet crewmembers assassinated the Chancellor. Kirk and McCoy are sent to a Klingon gulag, and the Enterprise crew must race the clock to clear their names by finding the real killers and securing peace between the Federation and the Empire.

Interesting bit
This movie contains cameos by actors from every Trek series except Enterprise (although the Klingon courtroom did make an appearance in an episode of the new series). Michael Dorn shows up as Colonel Worf (TNG), Rene Auberjonois shows up (uncredited) as Colonel West (DS9), and Kurtwood Smith shows up as the Federation President (VOY). Also of note is a cameo by Christian Slater as the communications officer on the USS Excelsior.