Spock's mother is dying and Spock returns to the planet Vulcan where he and Sarek enjoy a rare moment of rapprochement. But just as his wife's illness grows worse, duty calls Sarek away. Yet soon Sarek and Spock must put aside their differences and work together to foil a far-reaching plot to destroy the Federation - a plot that Sarek has seen in the making for nearly his entire career.
Time in the galaxy has stopped running its normal course. That can only mean one thing - the Guardian of Forever is malfunctioning. To save the universe, Starfleet command reunites three of its most legendary figures - Admiral James T. Kirk, Spock of Vulcan, and Dr. Leonard McCoy - and sends them on a desperate mission to contact the Guardian, a journey that ultimately takes them 5,000 years into the past.
The Romulans attack the planet Gateway, where Federation scientists are studying the Guardian of Forever - the mysterious portal to the past. The Enterprise must protect the Guardian ... or destroy it, but Spock has already used the portal to journey to the past. On the planet Sarpedion, 5,000 years ago, Spock knew a beautiful, primitive woman. Now he has gone back to meet his son!