AllMovie

The Enterprise becomes involved in a secret espionage mission to steal technology from the evil Romulans in this installment of the enduringly popular science fiction series. The covert nature of the mission forces Captain Kirk to act in a manner that to the crew appears unprofessional and downright bizarre, ordering the Enterprise to cross the border of the Neutral Zone, violating the Federation's treaty with the Romulans. The ship is soon captured by a Romulan fleet, and Captain Kirk and Mr. Spock are taken aboard the head vessel, where Kirk's irrational behavior continues. During their meeting with the Romulans, Kirk and Spock get into a violent confrontation, which appears to conclude with Spock's killing the captain in self-defense. Spock apparently assumes command, but this proves to be a ruse allowing Kirk -- who was in fact merely paralyzed -- to begin his real mission. With the help of several other high-ranking officers, Kirk attempts to investigate and hijack the Romulan ship's "cloaking device," a piece of technology that allows the Romulan ships to become invisible.