TOS Season 3 Episode 1 Spock’s Brain

Plot

The Federation starship USS Enterprise, under the command of Captain Kirk, encounters an alien ship, from which a mysterious woman beams onto the Enterprise bridge. She stuns the entire crew then examines each of them, taking particular interest in the Vulcan First Officer Spock. When the crew awakens, Chief Medical Officer Dr. McCoy finds Spock in sick bay with his brain surgically removed. Because of his unusual Vulcan physiology, Spock's body can be kept alive in this state for no more than twenty-four hours, giving Captain Kirk that much time to recover his stolen brain.
The Enterprise follows the alien ship's ion trail to the sixth planet of the Sigma Draconis system, a harsh world in the middle of an ice age. A band of male inhabitants attack the landing party, and a captured attacker warns Kirk about the "others", also known as "the givers of pain and delight". Kirk asks about the females of his kind, but is met only with bewilderment.
The landing party is joined by Dr. McCoy, accompanied by Spock's mobile body, controlled by a device McCoy has fashioned. The party travels deep underground and encounters a woman named Luma. When questioned, Luma shows the mentality of a child. Spock's voice is heard through a communicator, but before the conversation goes further, Kirk and his party are captured. The party is brought before the leader of the women, Kara, the same woman who appeared on the Enterprise bridge. Kirk demands to know what they have done with Spock's brain, but Kara claims not to understand what a brain is, exclaiming "Brain and brain! What is brain?"[1] As they try to explain the function of a brain, she realizes that what they are seeking is the "Controller", on which the underground civilization is completely dependent.
The landing party escapes and follow Spock's signals to a control room where his brain has been placed. Kara tells them that the skills needed to remove a brain were provided by a machine called the "Teacher", and that knowledge so obtained lasts no more than three hours. McCoy decides to use the Teacher himself, and then quickly begins the procedure to restore Spock's brain. McCoy's new knowledge begins to fade before the operation is complete, but Spock provides assistance after McCoy reestablishes Spock's ability to speak.
Without their Controller, Kara fears for the women's existence. Kirk assures Kara that the men and women can learn to survive together on the surface. Spock begins a long winded history of the culture of Sigma Draconis VI, much to the dismay of McCoy.