Admiral Kirk's defeat of Khan and the creation of the Genesis planet are empty victories. Spock (Leonard Nimoy) is dead and McCoy is inexplicably being driven insane. Then a surprise visit from Sarek, Spock's father, provides a startling revelation: McCoy is harbo ring Spock's living essence. With one friend alive and one not, but both in pain, Kirk (William Shatner) attempts to help his friend s by stealing the U.S.S. Enterprise and defying Starfleet's Genesis planet quarantine. But the Klingons have also learned of Genesis and race to meet Kirk in a deadly rendezvous.