Plot

Kirk, Spock, Abraham Lincoln and Vulcan legend Surak are pitted in battle against notorious villains from history for the purpose of helping a conscious rock creature's understanding of a concept he does not understand, "good vs. evil".

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. When Kirk refuses to continue after beating off a first traitorous attack, the creature ups the stake by causing a power disaster which will blow up the Enterprise in four hours unless they win.—KGF Vissers

Tracking down space legends of intelligent life leads the Enterprise to encircle a planet with a poisonous atmosphere and a molten rock surface (later known to them as Excalbia). As they're about to leave, they're probed and promptly greeted by former U.S. president Abraham Lincoln. Over Scott and McCoy's objections, this impossible personage is beamed aboard under military honors, after which Kirk and Spock agree to return to the planet with him. Excalbia, by this time, has transformed a section of itself into a habitable state, and it is there they meet up with Surak, the greatest Vulcan who ever lived. Now a true inhabitant of the planet appears, having set up a life and death "drama" to test out a concept alien to his people - good versus evil - pitting Kirk's group of four against another group of four composed of historical figures known for their notorious evil: genocidal war leader Col. Green, Kahless the Unforgettable of Klingon, conqueror Genghis Khan, and Zora of Tiburon who ran body chemistry experiments on tribespeople. Surmising that Kirk won't participant without proper incentive, the Enterprise is set to explode if his good group doesn't defeat the evil group in under four hours.—statmanjeff

When someone purporting to be Abraham Lincoln asks them to beam down to the planet below, Kirk and Spock agree to join him. Soon Surak, the greatest Vulcan of all time, is with them. They are told by a rock-like creature that they are there to do battle against four of history's most evil characters. The rock creature's society does not understand the concepts of good and evil and the battle between the two groups will determine which has the greatest merit. They are free to use any materials available to them on the planet and Kirk soon realizes that there are weapons to be made.—garykmcd

Tracking down space legends of intelligent life leads the Enterprise to encircle a planet with a poisonous atmosphere and a molten rock surface (later known to them as Excalbia). Spock finds evidence of a carbon based life-form on the planet surface, which is impossible given the circumstances of the planet's surface. All attempts to establish communications are met with no response. As they're about to leave, they're probed and promptly greeted by former U.S. president Abraham Lincoln (Lee Bergere). Lincoln wishes to be beamed aboard and tells Kirk that his ship would be directly overhead his position in 12.5 minutes. All of a sudden, an area of 1000 sq kms clears up the surface, with an oxygen/nitrogen atmosphere.

Over Scott and McCoy's objections, this impossible personage (Just before beaming Spock thinks he has locked onto a mass of living rock, with claws, which formed into a human form) is beamed aboard under military honors (full dress uniforms), after which Kirk and Spock agree to return to the planet with him. McCOy again protests as he thinks Kirk is being misguided by the form of Lincoln, who was Kirk's greatest personal hero of all times. Kirk is treating "this form" as the real thing when they all know that the real Lincoln died 300 yrs ago on Earth. Kirk agrees, but argues that the Enterprise exists to make contact with other life-forms. He decides to beam down with Spock. Excalbia, by this time, has transformed a section of itself into a habitable state, and it is there they meet up with Surak (Barry Atwater), the greatest Vulcan who ever lived. But McCoy and Scott notice that when Kirk and Spock beam down, their phasers don't beam down with them. They have their communicators, but they are being jammed.

Meanwhile the Enterprise loses all power, but no systems on-board the ship are damaged.. Now a true inhabitant of the planet appears (it is a lava based life form with claws), having set up a life and death "drama" to test out a concept alien to his people - good versus evil - pitting Kirk's group of four against another group of four composed of historical figures known for their notorious evil: genocidal war leader Col. Green (Phillip Pine), Kahless (Bob Herron) the Unforgettable of Klingon, conqueror Genghis Khan (Nathan Jung), and Zora (Carol Daniels) of Tiburon who ran body chemistry experiments on tribes-people. Surmising that Kirk won't participant without proper incentive, the Enterprise is set to explode if his good group doesn't defeat the evil group in under four hours.

Surak is against fighting, but Kirk insists that the Enterprise is at stake. Surak says perhaps it is their belief in peace that is being tested. Surak goes to Col Green to negotiate peace, but he is killed instead. Kahless imitates the voice of Surak to call out to Spock for help. Lincoln convinces Spock and Kirk to mount a frontal attack on Col Green, so he can go from the back to rescue Surak. But as this executes, Lincoln finds that Surak is dead and Green and Kahless capture him. A hand to hand battle ensues and Kirk and Spock emerge victorious. Kirk argues with the creature, about what gives him the right to hand out life and death. He says its his right to learn new things. Kirk and Spock are allowed to leave in peace. The ship is functioning normally again and the duo are beamed back aboard. The planet reverts to its normal appearance. Spock speculates that the beings on the planet have the power to arrange molecules in whichever way they see fit. They also scanned the human minds to pick the concept of good and evil and materialized them in the form of historical characters, which were based on the memories and thoughts of the people they scanned.