An unidentified ion-powered alien ship approaches the Enterprise
and refuses to identify itself. Even Scotty is impressed by its design and Spock determines a single humanoid lifeform is aboard. The lifeform beams aboard the bridge and appears as an attractive woman. When security guards arrive, she stuns everyone with her wrist bracelet, first on the bridge and then across the entire ship. Smiling, she examines first Kirk, then Spock.
Interesting design. I've never seen anything like her.
And ion propulsion at that. They could teach us a thing or two.
Everyone wakes up to discover that Spock is missing. McCoy calls Kirk down to sickbay and reveals that they have Spock’s body… but its brain has been removed using medical techniques beyond anything they know. McCoy notes that due to Spock’s Vulcan physiology, he can’t maintain his body for more then 24 hours.
Bones, what's the mystery?
His brain is gone. It's been removed surgically.
follows the ship’s ion drive but lose it in the Sigma Draconis system. There are three Class M planets, one with industrial technology similar to the 15th century, another one close to the year 2030 in design. The third planet has no industrial development and is glaciated, with only a primitive society. Uhura picks up regular energy emissions from the ice planet and Kirk decides of the three, it’s the most likely given that none of the three has the necessary technology.
What would they want with Mr. Spock's brain?
Why do they want it?
Yes. Why would they want it?
Kirk takes a landing party with Scotty, Chekov, and two security guards. The local primitives, all male, attack and they stun one man who talks about the Bringers of Pain & Delight. He doesn’t know what females are and refuses to take them there. Chekov detects ruins indicative of an ancient city and the primitive runs off in terror. Scotty finds a cave holding food and furs, and Kirk spots a light beam. He suspects it’s a trap to lure in the men and calls down McCoy, who arrives with the remote-animated body of Spock. Kirk plans for himself, Scotty, and McCoy to go into the cave and set off the trap, and they take Spock in. They break the beam, a metal door slams down, and the chamber descends down into the depths, while Chekov and the security guards keep watch above.
Who are the Others?
The givers of pain... and delight.
Underground, the doors open and they come face to face with a woman, who Kirk stuns before she can use her bracelet. McCoy revives her and the woman knows nothing about Spock’s brain or anything else. She identifies herself as Eymorg and McCoy notes that she has the mind of a child. They pick up a signal: Spock, talking to them and fully conscious. They start to move off but the woman from the ship arrives with two male slaves, and stuns them.
There she is. That's the one.
What have you done with Spock's brain?
Kirk and the others wake up and discover they have some kind of belt device on them. The woman, Kara, doesn’t know anything about Spock’s brain and McCoy notes it may be complete disassociation. They try to find out who controls the underground compound and Kara realizes they’re talking about their “Controller,” and she refuses to let them meet it once she realizes the brain they’re asking about is the Controller. Kirk tries to humble himself, realizing Spock is the Controller. Kara doesn’t buy it and tortures them using the belt devices. After she leaves, Kirk and the others try to get to their equipment and start a fight. Defeating the Morg guards, Kirk contacts Spock again and confirms he is controlling the entire facility. They lock onto Spock’s transmission and head toward it with Spock’s body in tow. Spock determines that the red button on the bracelet release the pain belts.
We just want to talk to somebody about Spock's brain.
Brain and brain! What is brain?
They come to the Control room and enter to find Kara present. She activates the pain belts but Kirk manages to use the remote to move Spock’s body (which doesn’t felt he pain) to attack Kara and release the belts. Kara insists Spock must stay to maintain the base for them but Kirk demands that she put the brain back. Kara has no idea and says that used the “Teacher” to give herself the Old Knowledge. Spock announces that she is referring to the taped storehouse of her ancestors. Kirk forces her under the helmet and she instantly becomes much smarter: smart enough to use a phaser on kill. Scotty fakes illness and distracts her so Kirk can disarm her.
That phaser is set to kill.
So it is. That is the knowledge you have brought me.
Kara refuses to help but McCoy insists he do it himself and hopefully retain the knowledge. Kirk agrees and McCoy dons the Teacher helmet. It inflicts pain on him but he manages to hold onto the knowledge and he begins the operation. Kirk explains to Kara that her and the other women will have to work with the males to survive on the surface. McCoy starts to lose the knowledge and tries to do enough work to hook up Spock’s vocal chords. Spock then directs him through the rest of the surgery using the knowledge he gained as the Controller and the day is saved.
A child could do it!