Defeating Khan is an empty victory for Admiral James T. Kirk. Spock is dead and McCoy appears to have succumbed to insanity. However, things might not be as grim as they seem and it is up to Kirk to save both of his friends.

Star Trek: The Voyage Home

To save Spock, Kirk has defied the rules once again, but as he is preparing to face the consequences, a new threat endangers Earth. Kirk and his crew have to embark on a time-travelling adventure to save the planet and everyone on it.