"A World Against Itself"
Captain Kirk briefs the executive officers on the Enterprise's latest mission, "Project Bira 3", in the conference room. "The third planet from the sun of system Bira" he says, showing the star system on a monitor. "An extraordinary quirk of development left a wide belt of radio-activity around the planet, dividing it in two. Thus, two distinct civilizations arose there! One, mentally proficient; The other, physical giants! The more advanced ones, the Stoyaks, finally invented craft to fly over the R-A belt and invade the Gardas territory! The fight is now 200 years old!" "You say we're to place ourselves at the service of both sides", McCoy says. "But doesn't that abrogate the prime directive, non-interference in developing planets?" "Not when both sides call you in, Bones" the Captain replies. He orders Mr. Spock and Mr. Scott to represent the Federation on the mission. "You couldn't have picked a better team", Scotty says as they prepare to beam down. "While Mr. Spock feeds his windy chatter to them brainy folks, I'll be makin' real human contact with them honest, straight-talkin' ones!"
On the surface, a pair of well-muscled men wearing animal skins greet the landing party. The leader of the Gardas introduces himself as Netuya, and welcomes them in peace. Netuya warns that the Stoyaks are coming, and suggests that he lead Spock and Scotty to his camp. "I think it is best to wait awhile longer, Netuya" Spock says.
While they wait, Scotty questions Netuya about the war. "How did your people hold out so long against flying craft and modern weapons?" he asks.
Uxorda tells Spock that peace with the Garda is impossible, because they are beasts. "Reason is unknown to them!" he says. Spock tells Uxorda that the Garda are "blessed with a natural power that reduces their need to study", but that they are intelligent. "How would you know that?" Uxorda asks. "Our calculations are that you yourselves are of low intelligence!" He leads the two men to a room containing large cylinders. "You could never comprehend the workings of these devices" Uxorda says. "Suffice it to say, we shall temporarily enlarge your brain capacity!" "I'd like to enlarge your head with my knuckles!" shouts Scotty. Spock and Scotty are forced into the cylinders, and the Stoyaks activate the device. (Just before the switch is pulled, Spock betrays a little emotion to Scotty, saying "Perhaps we will be fortunate, old friend!")
When they are removed from the cylinders, Scotty is able to solve complex math equations easily. When Spock is given the same test, he become violent and emotional. "What do I know of your stupid numbers, or care!" he says. "Your 'scientists' are just another form of tyrant!" The Vulcan strikes the test paper out of Uxorda's hand, and is struck unconscious with a pistol butt by one of the Stoyak guards. "How in the world did I get so smart, and he so dumb?", Scotty asks Uxorda. "We did underestimate Mr. Spock's natural intelligence" Uxorda replies, "Thus we gave him an overdose of the ray! The effect was to reduce his intelligence!" Uxorda pronounces Scotty the new leader of the Stoyak people. Meanwhile, Mr. Spock is taken to an underground dungeon, where he is placed in a cell with Netuya.
Later, when Spock awakens, he and Netuya talk in the cell. "So, you have felt the bite of the dogs, eh?", Netuya says. "You would never have believed me if I told you of the Stoyak cruelty, because you too, worship their god, science! You could never think ill of men with such minds!" "I spit on their science!" Spock replies angrily, "I am none of those! The blood of wild beasts runs in my veins! Vengeance shall be mine!" Later that night, Spock and Netuya trick their guards into coming near their cell, and overpower them.
After they escape, they leave the prison and journey into the dense jungle nearby. A huge, lion-like beast with a single horn on its head attacks the pair. Spock kills the beast by punching it in the face! "We have a legend" says Netuya, "The Garda shall be delivered from their enemies by 'Ibar the Magnificent', who shall announce himself by defeating a horned Mossek with his bare hands!"
Spock is pronounced the leader of the Garda people. "I will write my vengeance in Stoyak blood" Spock says, "and you are welcome to follow me!" At the same time, Scotty prepares to lead the Stoyak fleet in an attack against the Gardas. Meanwhile, back on the Enterprise, Captain Kirk leaves Mr. Sulu in charge of the ship, as he and Dr. McCoy beam down to the surface of the planet in order to locate Spock and Scotty, who are overdue.
On the surface, Scotty and the Stoyak air fleet come upon a Garda war party, led by Mr. Spock. The Stoyaks quickly attack the group.
Mr. Scott tries to kill Spock with a laser blast, but narrowly misses. "This Spock, is he not your friend?" asks the Stoyak in the cockpit with Scotty. "Aye, he was my friend", Scotty says, "but that d'na count now! The man's turned rogue! An enemy to all thought and progress! He must die!" "We Stoyak are raised to be firm in our defense of ideas" the Stoyak thinks to himself, "but this man Scott is cold and ruthless even by our rules!" Below, Spock orders all of the Gardas to concentrate their mental energy on Scotty's craft.
Kirk and McCoy arrive at the scene of the battle. The Captain grabs Spock just as the Gardas are about to destroy Scotty's craft. "You don't understand!" he yells, "that's Scotty you're about to bring down!" "It is you who do not understand, Captain", Spock replies, "But there is no time for talk!" "You're right", Kirk says, "No time for anything but... THIS!" The Captain punches Spock hard in the stomach, and the Vulcan falls to the ground. "What the devil's going on here?" McCoy asks. "Scotty and Mr. Spock have taken sides in the civil war!" Kirk says, "opposite sides!" Overhead, Scotty orders the Stoyak ships to retreat to their base, in order to get reinforcements.
"Their personalities have completely reversed!", McCoy says. "Scotty is the new champion of science, and..." "Mr. Spock has become a man totally ruled by his emotions!" Kirk finishes. "I don't know how it was done, but I know we've got to undo it!" He and the Doctor travel to the Stoyak palace, where Uxorda is honoring Scotty for his skill in battle. The two men are captured by Stoyak guards, and brought before Uxorda. "I'm Captain Kirk, Mr. Scott's commanding officer, and I've come to present an offer from the Garda!" he says.
"Let Spock and Scotty face each other in hand to hand combat, winner take all!" Uxorda refuses, but Scotty agrees to the challenge. "If I can't out think that dunce, I deserve to lose!" Scotty says.
The following dawn, Scotty (who is dressed in black tights and a purple cape) and Spock (clothed in animal skins) meet to fight each other. "You will fight until one surrenders or is unconscious!", Kirk tells the two men. "No, Captain Kirk!", shouts Uxorda, "Those rules will not do! They will fight until the death of one is accomplished! Otherwise there will be no fight!" McCoy protests, but Kirk accepts the terms of the fight. As they circle, Spock and Scotty taunt one another. "Prepare to leave your blood on this field, my slow-footed friend!", Spock says. "They're not half as slow as that thing you call your brain!", Scotty replies. "All right, you blasted egghead", Spock shouts, "die!" The Vulcan kicks Scotty hard in the stomach, knocking him down, and then leaps on top of him and prepares to smash the Engineer's head with his fists!
At that moment, the effects of the brain change begin to wear off. Spock and Scotty both come to their senses, amazed that they were trying to kill each other. "Traitors!" shouts Uxorda, "Stoyak warriors, shoot them!" The Stoyaks refuse, believing that "Scott-eee" is a god. "Brave Garda warriors" Netuya cries, "Blast the impostors with brain energy!" The Gardas also refuse to obey. "No, Netuya" a Garda says, "if they are not gods, they have taught us a lesson worthy of gods! We must have peace!" Kirk quickly steps in. "The choice is simple" he says, "peace or destruction at the hands of your own people! I don't think it should take you long to decide!"
Later aboard the Enterprise, Spock compliments Scotty. "Actually", the Vulcan says, "you made a rather good spokesman for pure, emotionless logic, Mr. Scott!" "And you could have been a real man of action", the engineer replies, "if you hadn't been handicapped with a genius brain!"