Plot

For bringing hostility into their solar system, a superior alien race brings Captain Kirk into mortal combat against the reptilian captain of an alien ship he was pursuing.

When a reptilian alien race known as the Gorn destroys an Earth colony, the Enterprise comes under attack by the Gorn vessel. Captain Kirk soon gives chase to the Gorn ship, leading them to an unexplored solar system, gradually (and dangerously) increasing speed. Kirk prepares to destroy the Gorn ship until another race of powerful aliens called the Metrons stops them and forces both captains to face off in mortal combat. The main purpose of this one-on-one duel is to solve their dispute, the winner will be released and the loser will be destroyed along with his ship and crew.—Anonymous

After an alien vessel attacks the Federation outpost, Kirk goes in hot pursuit with every intent of destroying the attacker. Spock advises moderation, but Kirk is dogged in his determination to teach them a lesson. When they enter an uncharted solar system, a superior being stops them and transports both captains to a planet where they are to engage in mortal combat. The reward for the winner is to have his ship go free while the loser will have his ship destroyed. Kirk's opponent, a Gorn, is a large lizard-like creature and much stronger than Kirk who must use his wits to defeat this new enemy.—garykmcd

Cestus III sends a message to welcome Kirk. Cestus III is a remote earth outpost but well stocked with friends and other things, so Kirk is happy to beam down with Spock, and some others to enjoy the hospitality. But, They have beamed into a trap.

An alien race, the Gorn, a reptilian species who resemble large crocodiles with sharp fangs and beehive eyes, have completely destroyed every living thing. Kirk's friends are all dead. During a shootout, Kirk and the five crewmen try to plan strategy. They attack Gorn formations with mortar fire and force them to withdraw. Meanwhile the Gorn ship attacks the Enterprise in orbit. Sulu is in command and attacks the Gorn ship with Photon torpedoes. The Gorn have fled in their ship. Kirk is angry. His friends and his men are dead. "We will chase them" Kirk says. The Enterprise chases the Gorn ship, after beaming Kirk and his team from the surface, to an uncharted section of the galaxy. Kirk wants revenge for the loss of life of his crew.

Both the Enterprise and the Gorn ship are frozen in space. A powerful voice comes on the loudspeaker while an eerie light is throbbing. It says "we cannot allow violence in our sector. we are the Metrons." Kirk debates this until he is gone. The Metron voice explains. "The two captains will fight and decide the fate of their ships." Spock and everyone are stunned. Kirk and the Gorn ship captain are transported to an Asteroid, which has materials to build a weapon and attack each other. But they cannot communicate with their ships. The Gorn is over 7 feet tall and powerful. Now Kirk fears for his life. He tries to set a trap for the Gorn by throwing rocks on him and trying to stab him, but this is a monster. Kirk hesitates a moment before killing him. The Gorn hurts Kirk's leg and Kirk is limping. Because the Metrons are powerful and civilized, they allow the rest of the crew to see Kirk die and to prepare themselves as well for death. But Kirk is not out of ideas. And Spock sees it too on the video monitor. The Gorn calls Kirk on the communicator and says that humans were intruding in their space by building a colony on Cestus III. McCoy is intrigued to learn that humans may be in the wrong in this situation.

Kirk finds sulfur, diamonds, coal and other things to make gunpowder and a missile launcher. Now Kirk is about to die and he lights a piece of his uniform on fire as a match and uses his translator as a flint. The cannon goes off, the video goes blank on the ship. Kirk's cannon worked and the Gorn is almost completely unconscious. Kirk grabs the Gorn's knife and is ready to thrust it into its neck. Then Kirk throws away the knife and says to himself "I won't kill you." Then he yells at the sky. "I won't kill him. The Gorn thought they were defending their sector. I won't kill him for you". The Gorn of course is almost dead anyway. Now Kirk relaxes waiting for the Metrons to kill them all. But they do not.

A Metron appears in a glistening shimmer. A young man, with blond hair, wearing a thin wispy robe, appears. He says "Why didn't you kill the Gorn?" And Kirk says "Maybe he was right in the fight. I don't know," The Metron says "You showed mercy. maybe you are worth having in the universe." Kirk smiles. The Metron says "In all honesty, I will kill the Gorn and his ship if you wish." Kirk says "No, we will work it out." Then Kirk is back on the ship. Spock says "What did the Metron say?" And Kirk says to Spock "He said we were a very promising species. Did you know that?" Spock says "I had my doubts." Then Kirk and all the human crew begin laughing including the yeomen.