Captain Spock has left Starfleet to become Ambassador Spock and has been bonded in a Vulcan engagement ceremony to his former protege, the beautiful Commander Saavik. Spock is on a minor diplomatic mission when a call from an old enemy, now a friend, sends him off on a dangerous mission to the planet Romulus, peopled by a volatile and emotional offshoot of his own stoic Vulcan race. Romulan society is facing collapse unless Spock and Saavik can put aside their powerful Vulcan Pon Farr mating drives for long enough to warn the Klingons of a dastardly attack on the outpost at Narrendra III.

Meanwhile, Captain Jean-Luc Picard, in command of the USS Stargazer, is sent to infiltrate Romulan territory and recover Spock and Saavik. But is Picard's real task to aid them or to stop them completing their mission, which has put the peace of the galaxy at risk?