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The Enterprise encounters a curious ship of unusual design. Upon contact, the ship emits a transport beam and a mysterious woman appears on the Enterprise bridge. She stuns the entire crew using a bracelet-like device, 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 lying on a bed in Sickbay with his brain surgically removed.

Thankfully, owing to his unusual Vulcan physiology, Spock's body can survive in this "brainless" state mechanically, giving Captain Kirk about 24 hours to find his stolen brain. Sensors detect the ship's ion trail and Kirk follows it to the Sigma Draconis system. The system contains three planets that are reported to be inhabited: Sigma Draconis III, IV and VI.

However, the recorded technological levels of each world are determined to be incapable of producing the kind of spacecraft that the Enterprise followed here. The sixth planet however, which shows no sign of industrial advancement at all, radiates energy transmissions that Communications Officer Lt. Uhura states as contradictory to its technological scale. Playing on the hunch that the planet may be deceiving, Kirk beams a landing party to the surface.

Sigma Draconis VI is revealed to be a harsh world in the middle of an ice age, but the landing party has no trouble locating the local inhabitants, who attack them on sight, believing them to be "The Others". Kirk captures one of the attackers and questions him. The man identifies himself as a Morg and warns Kirk about the "givers of pain and delight". Kirk asks the Morg about the females of his kind, since there were none around, but is only met with the man's bewilderment. Kirk asks the Morg to help him find "the others", but he refuses and runs away.

The landing party soon comes upon the ruins of a buried city: here they find an elevator that leads underground. Kirk calls Dr. McCoy down from the Enterprise, who has fashioned a device to remotely operate Spock's brainless body and has the mechanically controlled Spock accompany him. The team heads down and they encounter a woman named Luma who tries to activate her bracelet, but Kirk quickly stuns her with a phaser. When questioned, Luma shows she only has the mentality of a child.

Spock makes contact with the landing party through a communicator, but before anything can be done, Kirk and his party are apprehended by Kara, the same woman who appeared on the Enterprise bridge. She identifies herself as the leader of the Eymorgs, the apparent females of the Morg. The Eymorgs place belts on the Enterprise landing party that they can't remove and that inflict intense pain upon them. Kirk demands to know what the Eymorgs have done with Spock's brain, but the frustrated Kara responds with, "Brain and brain, what is brain?"

McCoy informs Kirk that if all the Eymorgs have such a low intelligence that they couldn't possibly be capable of removing a brain the way Spock's was removed. Someone, or something else must be behind all this.

The landing party manages to overpower their guard and follow Spock's instruction to the central "controller" which is actually his brain kept alive in a black box that is tied to a control panel. Here, they also find Kara, who immediately immobilizes the team using the pain belts. Kirk uses the remote that controls the mechanically operated Spock and makes him grab Kara's wrist and press the release button on her bracelet. Once free of the pain, Kirk listens to Spock's brain via communicator. They realize that Spock is now the "Controller" - a living computer that the Eymorgs hope will last 10,000 years.

Spock says he operates the power systems of the planet, recirculating the air, running heating plants and pumping water - all functions that require a supreme intelligence for the regulation of a planet-wide life support system. He also informs them that the Eymorgs can gain temporary understanding of ancient knowledge from a machine called "the Great Teacher" to which Kara leads them. Kirk forces Kara to use the Teacher, hoping it will teach her the techniques necessary to replace Spock's brain. After using the machine to boost her intelligence, Kara instead uses a phaser to threaten Kirk. Chief Engineer Scott pretends to faint and Kirk uses the distraction to grab Kara's phaser.

McCoy then tries the Teacher on and discovers how to perform a "reverse brain transplant" on Spock. McCoy conducts the surgery and nearly manages to do so within the three-hour time limit that the implanted knowledge lasts. However, the knowledge leaves McCoy before the operation is complete. Mr. Spock provides some assistance himself after McCoy reestablishes Spock's capacity to speak verbally.

Without their Controller, the Eymorgs fear for their existence. Kirk then informs Kara that the Eymorgs will have to take their chances on the surface and live as the Morgs do. He suggests the two societies can share "the Teacher" device and learn together. Kara is not overly enthusiastic about the prospect, but Kirk at least offers some assistance.[1]

Errors and ExplanationsEdit

The Nitpicker's Guide for Classic TrekkersEdit

Plot OversightsEdit

  1. In the society on Sigma Draconis VI, men live on the surface and women live below. Supposedly it's been this way for thousands of years. Presumably the women mate with the men that they have taken as slaves and produce offspring. Do those offspring remain below with their mothers? If they do, how do the men on the surface procreate? When the children grow to a certain age, are the males banished to the icy region above? A small number could be kept as breeding stock.
  2. Why have the females deteriorated and lost the knowledge? ls it because they're females? They need a man's brain to tell them what to do? More likely they haven't needed to use the knowledge before.
  3. Alter Kirk forces Kara to don the Teacher, she takes on a new persona—one of great calm and intelligence. Then she reaches under her skirt and pulls out a phaser. Scott notes that the phaser is set to kill, and Kara replies that the Teacher gave her the knowledge to operate the device. She does not seem surprised that the phaser is set to kill. In fact, she apparently wants the phaser on “kill.” Note that Kara—from the time she pulls the weapon out of her skirt—never touches the setting. Also note that Kirk had the landing party set their phasers to stun. Therefore, when Kara confiscated the phasers, they were set on stun. Some time later, she set the phaser to kill and she did it before she received another dose of knowledge from the Teacher! lf the Teacher is her only source for knowledge about the weapon, how did she know how to change the setting? Natural instinct, perhaps?
  4. Trying to convince Kirk to allow him, to don the Teacher, McCoy says he might be able to retain some of the medical techniques and bring them to the “world.” Which world? Wouldn't McCoy say that he might bring them to the “Federation” or the "galaxy"? ' Of course, when McCoy loses the knowledge of the Teacher, the simple solution would be for another member of the landing party to submit to the device. Instead, Kirk allows the doctor to bumble along with his natural abilities. There isn't time for someone else to swap places with McCoy, who in any event is the best qualified to carry out surgical procedures.
  5. Does Spock have a flip-top head? Twice in this show he has major cranial surgery and his hair looks perfect immediately afterward. The knowledge McCoy received from the Teacher must have included a technique to minimise scaring.

Equipment OdditiesEdit

  1. While trying to decide which M-class planet to visit in search of Spock's brain, Kirk looks at the back of the bridge on two different occasions and quotes how much time he has left. lt’s like he's looking at a clock, but I don't recall ever seeing a timepiece in that location. Kirk could be reading the time from something that does not obviously resemble a timepiece that we would recognise.
  2. To make it easier to take Spock’s body along during the search for the Vulcan’s brain, McCoy and Scott rig a remote control device. With it, they march Spock’s body around like a robot. (I had a fleeting thought that Nurse Chapel might want to get her hands on that remote for an afternoon, but that's not really the main issue here.) Whenever Spock's body moves, it makes a clicking sound. Why is it making a clicking sound? Does he need a little oil in those knee joints? The clicking could be from mini servos, implanted to boost the signals from the remote control device.

Nit CentralEdit

  1. Alan Hamilton (Alan) on Sunday, June 10, 2007 - 11:10 pm: Equipment oddity: when they beam down, Kirk says "Suit temperatures to 72" and everyone reaches behind their backs like they're adjusting something. Apparently the uniforms have heaters built-in. Sulu could have used that in The Enemy Within. The self heating uniforms could have been developed specifically because of the events in The Enemy Within.


  1. See The Original Series category entry.


  1. Spock's Brain at Wikipedia

The Original Series Season 3
Spectre of the Gun I Elaan of Troyius I The Paradise Syndrome I The Enterprise Incident I And the Children Shall Lead I Spock's Brain I Is There in Truth No Beauty? I The Empath I The Tholian Web I For the World Is Hollow and I Have Touched the Sky I Day of the Dove I Plato's Stepchildren I Wink of an Eye I That Which Survives I Let That Be Your Last Battlefield I Whom Gods Destroy I The Mark of Gideon I The Lights of Zetar I The Cloud Minders I The Way to Eden I Requiem for Methuselah I The Savage Curtain I All Our Yesterdays I Turnabout Intruder