The Enterprise's sensor readings indicate a planet unsuitable for any carbon-based life at the level of a developed civilization. Suddenly they get an apparition in space from someone who looks like and claims to be Abraham Lincoln. He insists on them checking him out and coming over to a small part on the planet surface (which has suddenly developed a perfect atmosphere for humans). He is received with full presidential honors and Kirk and Spock agree to beam down with him, but as they do, phasers and tricorders fail to dematerialize with them, and communicators won't work. There they meet Surak, the greatest Vulcan of all time, equally convincing. The quartet is greeted by a creature consisting of molten rock who presents them to notorious historical villains Ghengis Khan, Colonel Green, Zora and the Klingon Kahless the Unforgettable. They're told the teams represent good versus evil and must battle to the death against each other to teach the creature their concept.