Stardate 3045.6: While in orbit above an isolated Federation outpost on Cestus III, Kirk, Spock, McCoy, and a few tactical officers beam down for a visit but soon discover that the outpost has recently been destroyed. Outnumbered, the landing party must fight off a mortar barrage from alien troops while looking for survivors. The Enterprise, meanwhile, is attacked by the alien's vessel and is compelled to disengage. Kirk finds the outpost's arsenal and, with the help of a Starfleet mortar, manages to halt the alien ground attack and force the aliens to transport back to their vessel. The landing party beams back to the Enterprise which begins pursuing the alien ship. Kirk decides that the alien surprise attack cannot go unpunished and becomes determined to destroy the attackers. The chase becomes a test of engineering capabilities for both sides as each ship pushes the limits of their warp drives. Suddenly, both ships are subjected to scanning beams and then brought to a complete stop with tractor beams from a nearby solar system inhabited by an advanced raced called the Metrons. The Metrons, who dislike trespassers and the violent intents of both the humans and the Gorns that they pursue, decide that the incident shall be settled in a different fashion and transport Kirk and the Gorn captain to an uninhabited asteroid where they will fight to the death. The winner will be free to leave while the loser, along with his ship and crew, will be destroyed in the interests of peace. Kirk then gets his first look at the Gorn captain, a very intelligent but equally powerful, lizard-like creature. During the contest, Kirk narrowly escapes the Gorn's attempt to trap and kill him with a chiseled dagger, and manages to combine the asteroid's mineral resources into gunpowder which he uses in a cannon-like weapon to wound the Gorn captain. When Kirk refuses to kill the Gorn, a Metron appears and states that Kirk surprised them by displaying mercy to an enemy that certainly would have killed him. Because Kirk spared his opponent, the Metron concedes that there may be some hope for Kirk's species after all and allows both captains to return to their vessels and vacate the area.