Set in the 23rd century, where Earth has survived World War III and then moved on to explore the stars. Kirk, Spock and Dr. McCoy are transported to the 1930s, where Kirk falls in love with a doomed peace activists. The Enterprise finds itself docked at the same space station as the Klingons and tensions soon escalate into a full-scale barroom brawl. For the first time, the Enterprise crew battle their enemies the Romulans, who have a cloaking device that renders their ship temporarily invisible. A glimpse into Vulcan culture and Spock must mate or die.