Branded as fugitives by the very federation they swore to protect, the crew of the U.S.S. Enterprise dutifully returns to Earth to face charges for crimes committed in the course of rescuing a resurrected Spock. But en route, it is learned that the Earth is being ravaged by a strange alien probe demanding a response from a life form that no longer exists. Commandeering a captured Klingon Bird of Prey, Kirk and his crew bend time and space to save Earth and rediscover the meaning of friendship.