• Production Code: 77
• Stardate: 5906.4
• Original Air Date: Mar 7, 1969
• Writer: Arthur Heinemann and Gene Roddenberry
• Director: Herschel Daugherty
• Guest Stars:
  • Lee Bergere (Abraham Lincoln)
  • Barry Atwater (Surak)
  • Phillip Pine (Colonel Green)
  • Arell Blanton (Chief Security Guard)
  • Carol Daniels DeMent (Zora)
  • Robert Herron (Kahless)
  • Nathan Jung (Ghengis Khan)

Over the planet Excalbia, the Enterprise is intercepted by who appears to be Abraham Lincoln, floating through space. Beaming aboard, Lincoln is welcomed by Kirk, who is somewhat awed by the presence of one of his most revered figures of history. "Lincoln" extends an invitation to Kirk and Spock to visit the planet, whose normally lava-covered surface sprouts a zone of Earthlike safety just for the landing party. Kirk, Spock and Lincoln are joined on the surface by an image of Surak, who initiated the doctrine of emotional restraint on Vulcan. A rock-creature appears and introduces Kirk and Spock to four more illusionary figures from history, this time the fiercest conquerors, tyrants and villains of the past, from Earth's Genghis Khan to Kahless the Unforgettable, who, as Surak did for Vulcan, set the standard of behavior for the Klingons. The creature pits the best and most noble - Kirk, Spock, Lincoln and Surak - against the most vile historical figures. The rewards for Kirk and Spock, should they survive, are their lives, and the lives of everyone aboard the Enterprise.