Captain Kirk (William Shatner) leads his crew on a mission to free kidnapped diplomats. Arriving at the planet Nimbus III, Kirk and crew come face-to-face with the captor: a smiling Vulcan named Sybok (Laurence Luckinbill) who's Mr. Spock's half-brother. Obsessively searching for God, Sybok hijacks the Enterprise and sets a course for the center of the galaxy. The film marks Shatner's directorial debut.