Trama

The crew of the Enterprise pursues a mysterious woman who has abducted Spock's brain.

The Enterpise is approached by an ion-propelled craft (much to Eng. Scott's liking); from it enters a female who renders everyone unconscious. When the crew wakes up, McCoy finds Spock alive in sick bay but with his brain surgically removed. McCoy urges its quick restoration if he's to survive at all. Desperately Kirk follows an ion-trail to a system where he gambles on an icy planet populated by a simple-minded all-male race of large cavemen who attack them. The landing party captures one, who says Kirk and crew are small like 'The Others' - bringers of pain and delight - whom they fear. McCoy brings down Spock's body, mobilized with a mechanical brain-substitute installed. They enter the acclimatized, underground dwelling of 'The Others' - a similarly simple-minded all-female race of enslavers - and overpower female Luma by surprise. Kirk makes communicator contact with Spock, who knows not where he is but is aware of autonomic functions. As they finally find Kara, the female brain-thief, she overpowers them and, outfitting them with control belts, brings them before a female panel to be judged. As their interrogation commences, they realize there is no superior intellect among them capable of handling the technology to maintain the subterranean complex, and the 'controller' to which these women begin to refer is actually Spock's brain, which Kirk must somehow get back and reunite with Spock's body.—KGF Vissers

When the Enterprise encounters an ion-powered vessel - far more advanced than their own warp-powered technology - they soon find themselves knocked unconscious by a beautiful alien who suddenly appears on the bridge. When they come to, they find that Spock's brain has been surgically removed using technology way beyond their own current level of development. Following the ion trail left by the spacecraft, they arrive at a barren, ice-covered planet where the men live on the surface and the women in a highly advanced underground complex. Spock's brain is now the central intelligence that runs the entire complex. The problem before them: how to reunite his brain to his body.—garykmcd

An unidentified humanoid female from a seemingly advanced civilization transports aboard the Enterprise and, after rendering the entire crew unconscious, absconds with Mr. Spock's brain. Kirk must pursue her and retrieve Spock's brain before the life support systems keeping his body alive fail.—Anonymous

Captain James T. Kirk (William Shatner): The commanding officer of the USS Enterprise Commander Spock (Leonard Nimoy): The ship's half-human/half-Vulcan science officer and first/executive officer Lieutenant Commander Dr. Leonard "Bones" McCoy (DeForest Kelley): The ship's chief medical officer Lieutenant Commander Montgomery "Scotty" Scott (James Doohan): The Enterprise's chief engineer and second officer Lieutenant Uhura (Nichelle Nichols): The ship's communications officer Lieutenant Sulu (George Takei): The ship's helmsman Ensign Pavel Chekov (Walter Koenig): A Russian-born navigator introduced in the second season premiere episode Nurse Christine Chapel (Majel Barrett): The ship's head nurse.

The Enterpise is approached by an ion-propelled craft (much to Eng. Scott's liking); from it enters a female who renders everyone on the bridge unconscious. When the crew wakes up, McCoy finds Spock alive in sick bay but with his brain surgically removed. McCoy urges its quick restoration if he's to survive at all. McCOy gives Kirk 24 hrs for the whole thing.

Desperately Kirk follows an ion-trail to a system where he gambles on an icy planet (which shows signs of primitive life, but cannot launch sophisticated interstellar travel) populated by a simple-minded all-male race of large cavemen who attack them. The landing party captures one, who says Kirk and crew are small like 'The Others' - bringers of pain and delight - whom they fear.

McCoy brings down Spock's body, mobilized with a mechanical brain-substitute installed. They all enter the acclimatized, underground dwelling of 'The Others' - a similarly simple-minded all-female race of en-slavers - and overpower female Luma (Sheila Leighton) by surprise. Kirk makes communicator contact with Spock's brain, who knows not where he is but is aware of autonomic functions. As they finally find Kara (Marj Dusay), the female brain-thief, she overpowers them and, outfitting them with control belts, brings them before a female panel to be judged.

As their interrogation commences, they realize there is no superior intellect among them capable of handling the technology to maintain the subterranean complex, and the 'controller' to which these women begin to refer is actually Spock's brain, which Kirk must somehow get back and reunite with Spock's body. Kara refuses to let Kirk step anywhere near the Controller, who Kirk suspects to be Spock's brain.

Kara and the other females leave. Kirk uses his communicator to reach Spock again and uses his coordinates to reach him, with his body. Kara is in the room with Spock's brain and she again freezes Kirk and his men, with her control belts. Kirk uses the mechanical Spock body, which is unaffected by the control belt, to attack Kara and destroy the controller command module in Kara's hand. Kara insists that Spock should stay as the controller for 10000 yrs as the old controller is finished. Kirk wants Kara to put back Spock's brain in his body, but she claims she doesn't know how to. She says she used the Teacher to give her "Old knowledge".. The teacher is a helmet shaped device, wearing which gives one knowledge of complex procedures which a person may not even be trained on.

Kirk uses the helmet to "transfer" the teacher into Kara's mind, which is essentially all the knowledge of the old ones stored in the memory banks of their computers. Krik insists that the teacher puts back the controller (Spock's brain) back into his body. But the teacher says that his people's need for the controller is greater than Kirk's need for his friend. He refuses. So, Kirk decides to put the helmet on McCoy and transfer the Teacher's knowledge in McCoy, to perform the surgery to put back Spock's brain into his body. Midway through the operation, McCoy loses the knowledge of the teacher, and has to proceed with his own medical knowledge to save his friend. But by then Spock gains control of his speech and guides McCOy through the rest of the operation. Spock is back again. Kirk advises Kara to collaborate with the men above and relocate to the surface to build a new society. Spock inform the group that the ancient civilization was far advanced, but perished in face of a ice age of the planet. They built underground cities for the women and the men remained on the surface and male-female schism occurred.