In 2293, a shock wave strikes the starship USS Excelsior, commanded by Captain Hikaru Sulu, who discovers that Praxis, a Klingon moon, has been destroyed. The loss of Praxis and the destruction of the Klingon homeworld’s ozone layer throws the Klingon Empire into turmoil. The Klingons can no longer afford war with the United Federation of Planets, so they pursue peace. Starfleet sends the USS Enterprise-A to meet with the Klingon Chancellor Gorkon and escort him to negotiations on Earth. Captain James T. Kirk, whose son David was murdered by Klingons, opposes conciliation and resents the assignment.
Enterprise and Gorkon’s battlecruiser rendezvous and continue towards Earth, with the two command crews sharing a tense meal aboard Enterprise. Later that night, Enterprise appears to fire torpedoes at the Klingon ship, disabling its artificial gravity. During the confusion, two men wearing Starfleet spacesuits beam aboard the Klingon ship, kill two Klingon crew and grievously wound Gorkon before escaping. Kirk surrenders to avoid armed conflict and beams aboard the Klingon ship with Doctor Leonard McCoy in an attempt to save Gorkon’s life. The chancellor dies, and Gorkon’s chief of staff, General Chang, arrests and tries Kirk and McCoy for his assassination. The pair are found guilty in the trial and sentenced to life imprisonment on the frozen planetoid Rura Penthe. Gorkon’s daughter Azetbur becomes the new chancellor, and continues diplomatic negotiations; for the sake of security, the conference is relocated and the new location is kept secret. While several senior Starfleet officers want to rescue Kirk and McCoy, the Federation President refuses to risk full-scale war, even if the Federation stands a good chance of winning. Azetbur likewise refuses to invade Federation space.
Kirk and McCoy arrive at the Rura Penthe mines and are befriended by a shapeshifter named Martia, who offers them an escape route; in reality, it is a ruse to make their arranged deaths appear accidental. Once her betrayal is revealed, Martia transforms into Kirk’s double and fights him, but is killed by the prison guards to silence any witnesses. Kirk and McCoy are beamed aboard Enterprise by Captain Spock, who had assumed command and undertaken an investigation in Kirk’s absence. Determining that Enterprise did not fire the torpedoes and that the assassins are still aboard, the crew has begun a search for them. The two assassins are found dead, killed by yet another unknown accomplice. To bait the third accomplice, Kirk and Spock announce to the ship that the assassins are still alive and will be interrogated. When the culprit arrives in sick bay to finish them off, Kirk and Spock discover that the killer is Spock’s protégé, Valeris. To discover the identity of the other conspirators, Spock initiates a forced mind-meld, and learns that a cabal of Federation, Klingon, and Romulan officers conspired to sabotage the peace talks. The torpedoes that struck Gorkon’s cruiser came from Chang’s ship which has the unique ability to fire its weapons while cloaked.
Enterprise and Excelsior race to Khitomer, the location of the peace talks. Chang’s cloaked ship attacks and inflicts heavy damage on both ships. At the suggestion of Uhura, Spock and McCoy modify a torpedo to home in on the exhaust emissions of Chang’s ship. The torpedo impact reveals Chang’s location, and Enterprise and Excelsior destroy his ship with a volley of torpedoes. The crew from both ships beam to the conference and thwart an attempt on the Federation President’s life.
Starfleet Command orders Enterprise to return to Earth to be decommissioned. Kirk decides to take his ship on one last cruise and notes in his log that a new ship and crew will carry on their legacy.
Star Trek Command 