"The Animal People"
The Enterprise responds to a distress call from the planet Hercula, and a landing party beams down to the surface. Emperor Lidoro tells Captain Kirk that beasts, known as "Yerbas" have become mad and are fashioning weapons to threaten the population of the planet. The Emperor takes the landing party to a zoo, in order to see some of the Yerbas. They appear to be human! Lidoro explains that some freak of nature has made them look intelligent - but that they are still only animals. While the crew watches, two of the Yerbas attack each other viciously, and a guard separates them with a stun gun. Spock is curious why such advanced looking creatures would behave so violently. Lidoro tells him that packs of wild Yerbas are killing the livestock, and even the citizens! Kirk says that he must wait for orders from H.Q. before giving military assistance.
Back in the city, the landing party receives approval from Starfleet command to use force to put down the "animal" uprisings. Kirk asks Lidoro why his son Jivi does not want to lead the attack. Lidoro explains that Jivi was taken in by the Yerbas as a boy when he was lost, and was released unharmed. Ever since that day, he has refused to fight them. Kirk goes with Colonel Mynota to oversee the conquest of the Yerbas.
The Enterprise crew returns to the palace to find that Germal has repented, and will record the message of surrender to her people. As she begins the message, the Emperor asks Colonel Mynota what she is saying. He assures the Emperor that it is safe. At dusk, a squad of aircraft lay down a "square cloud of floating, reflective material" in the sky near the Yerba encampment. Another ship then plays the sign language message that Germal has recorded. The Emperor has been tricked! Germal's message to her people was not one of surrender, but of war! The Yerbas attack town after town ferociously.
The Emperor confronts the Colonel. Mynota claims again that the message was for peace, but Spock accuses him of letting a call to arms go out, so that he could kill all the Yerbas. The Emperor orders all Yerbas exterminated. Jivi refuses to assist the slaughter, and tells his father that his truth is "built on a foundation of lies - and slavery!" Kirk agrees, and withdraws all support for the campaign against the Yerbas. Emperor Lidoro orders Jivi and the Enterprise crew be taken prisoner. They are imprisoned deep beneath the palace.
Kirk suggests that Jivi and Germal get married in order to stop the bloodshed. They are surprised at his idea, but agree. Kirk utters the words "By the powers vested in me by the Federated Planets as Starship Chief Executive, I pronounce you man and wife!", and the ceremony is complete.
The scroll says that Hercula is not his people's native world. 10,000 years ago they had migrated from their dying planet, and made slaves of the inhabitants. The Yerbas had resisted, and been wiped out - except for the children, who underwent surgery to remove their speech and memory. As the Emperor is reading, Colonel Mynota breaks into the room and places the Emperor under arrest for "divulging the sacred scrolls to unworthy ones." He takes the scrolls and prepares to burn them, but Kirk hits him with a straight right hand and knocks him down.
Jivi and Germal slip away in the commotion. As the war on the surface rages on, the two begin broadcasting a message to the entire world from the Tomb of the Great Ones. "You have been told that Yerbas are animals - to be enslaved!" Jivi says. Germal repeats the message in sign language for her people as well. "We joined together to save both our people! This morning we were married. Five minutes ago - we drank the milk of the nua thorn! In a few seconds we shall be..." The last word is unspoken, but as the two bodies slump backward, the meaning is clear.
The Yerbas and Herculas throw away their weapons and pledge peace to one another. The Emperor agrees to share his throne with a leader elected by the Yerbas. He shows the Enterprise crew two things before they leave. The first is a statue of Jivi and Germal at the highest point of the planet - to remind his people of the cost of peace. The second is a newborn Yerba child with it's speech center intact, the terrible operations having been banned forever. "Atta' way boy!" Says Scotty to the crying child, "Keep on yelling as loud as you can! They paid a heavy price for your voice!"