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Nurse Chapel's long-lost fiance is found - along with his androids.



Exo III underground entrance

View of the surface from the underground ruins on Exo III

The USS Enterprise approaches the planet Exo III to learn the fate of Dr. Roger Korby, a prominent scientist whose last message was sent over five years earlier. Two previous expeditions have failed to uncover any trace of the Korby expedition.

Despite the odds, Korby and at least part of his expedition have survived by taking refuge in underground ruins left by the former inhabitants of the planet. Lieutenant Uhura picks up a transmission from Korby on the planet's surface, surprising the Enterprise crew.

Act One[]

Korby requests that Captain Kirk beam down alone, explaining that he has made discoveries that may require an extraordinary decision on Kirk's part. But when he learns Christine Chapel, his former fiancée, is aboard, he readily agrees for her to accompany Kirk.

Korby and Chapel reunited

Korby and Nurse Chapel reunited

Kirk and Chapel beam down, but are met by no-one, so Kirk has two security officers beam down as well. One security officer, Rayburn, is instructed to remain at the beam-down location while Kirk, Chapel, and the other security officer, Mathews, explore the ancient ruins, searching for Korby. Shortly after they meet Dr. Brown, Dr. Korby's assistant, Mathews falls into a "bottomless" cavern, leaving Kirk and Chapel alone. Unseen by them, a massive, Human-like figure moves away further into the cave system. Dr. Brown seems somewhat detached and aloof, barely reacting to Mathews' tragic fall. He also seems slow to recognize Chapel. Kirk contacts Rayburn at the cave entrance, informing him of Mathews' death and telling him to remain where he is and tell Spock to put a full security party on standby. But before Rayburn can carry out this order, he is attacked by the figure from the caves. Making their way through the winding cavern, Dr. Brown explains that the previous civilization that inhabited Exo III moved underground when their sun went dark. He elaborates that the inhabitants replaced freedom with a mechanistic culture and claims that once Dr. Korby is freed from the cavernous environment they are currently in, the discoveries he has made will revolutionize the universe. The group then enters an area furnished like a living room, which would appear to be the Korby expedition's living quarters. Inside, they also meet Andrea, a beautiful woman who wears a revealing blue and green jumpsuit.

Kirk and Andrea, android shield

"Drop it!"

Kirk meets Korby, who seems friendly enough. But he insists there be no communication with the ship. This is not acceptable to Kirk, especially since in addition to the death of one crewman, he has also lost contact with another, Rayburn, whom he left at the cave entrance. When Brown threatens Kirk with a laser pistol, there is a brief struggle during which Brown is shot – and it is revealed that he is not Human, but a complex android. Meanwhile, the massive android Ruk (the figure from the caves) immobilizes Kirk by picking him up and lifting him against a wall, preventing his escape.

Act Two[]

In another room, Korby has Ruk, in a near-perfect imitation of Kirk's voice, send a message to the Enterprise through Kirk's communicator, where Spock had been concerned that Kirk's routine check-in time had past. Korby warns Kirk that if he moves or cries out to Spock, Ruk will have no choice but to harm him. "Kirk" informs Spock that everything is fine and to maintain routine contact and signs off. Korby informs Kirk that Ruk had been tending the machinery in the ruins for longer than even he could remember. With his help and with the records Korby found, they built Brown. When directly asked by Kirk the fate of his second security officer Rayburn, Korby informs Kirk that Ruk killed both Rayburn and Matthews, but Korby claims it was expressly against his orders. Korby has Ruk imitate other voices, but grows angry when Ruk imitates Chapel. He orders Ruk never to mock or harm Chapel, and at Kirk's prompting, adds that he is to obey all of Chapel's commands. Kirk attempts to once again escape but Ruk is too fast for him. The hulking android picks him up and throws him across the room like a doll.

Andrea and Ruk operate controls

Androids behind the controls of the android duplicator

Korby returns to the main dining room to join Chapel and Andrea. Kirk is being held securely by Ruk as Korby begins to reveal more of his plans to Kirk and Chapel. Korby then reveals to them that Andrea, too, is an android and tries to convince a jealous Chapel that there is no romantic feelings between him and Andrea. Korby explains that Andrea simply obeys his orders, nothing more. To prove his point Korby orders Andrea to kiss Kirk, which she does, then to slap him across the face. But Kirk still demands answers: if these "mechanical things", as Kirk dubs the androids, say and do only as Korby programmed, then why did Brown tried to shoot him earlier and why did Ruk murder the two security officers? Kirk says that there are many things he still doesn't understand regarding everything that has been happening. Korby tells the captain that he will answer all of Kirk's questions now. A short time later, Korby leads Chapel to his laboratory where the android duplicator, with a Human-shaped blank that Ruk just locked down, mid-torso, on the side facing her, catches her attention. Korby informs her that this is how an android is made, then orders Andrea to slightly turn the circular, turntable-like platform. Chapel is shocked to see on the other side Kirk, naked, unconscious, and locked down by Ruk in a similar manner.

Act Three[]

Kirk is then spun around on the platform to be copied, while a shocked Chapel looks on in confusion. Soon the physical process is completed. Korby says the android is an exact physical replica of the real Kirk. He then explains that he will transfer all of Kirk's memories into the android to make the duplication complete. But Kirk overhears this, and while Korby readies the machine, Kirk murmurs to himself, "Mind your own business, Mr. Spock, I'm sick of your half-breed interference, do you hear?" He repeats this as the memories are copied. Korby then presents his new android to Chapel. "How do you do, Miss Chapel?"'

Kirk and his android duplicate

"Kirk" and Kirk at lunch

After the experiment, "Kirk" – in Starfleet uniform – joins Chapel for lunch, and asks her if she would obey if he gave her an order to betray Roger Korby. Chapel says, "Please don't ask me to make that choice." The tone of the conversation causes her to lose her appetite, but she encourages "Kirk" to eat. With a smile, he informs her that "Androids don't eat, Miss Chapel." She had been unknowingly talking to the android Kirk all along. Korby, Ruk, and the real Kirk, who is wearing a blue and green jumpsuit identical to Korby's, enter and even Kirk is impressed. He quizzes his duplicate on details of his life and family, but the android answers every question perfectly. The duplicate Kirk is sent to the Enterprise to secure the command packet from Kirk's quarters containing the ship's itinerary; Korby's plan is to select a colony where he can begin carefully manufacturing android replacements. He believes he can secretly create a superior android civilization, and he plans to prove it.

Kirk's stalactite

"Christine, is that you?"

Kirk makes a third attempt to escape by choking Korby with a cord from the underside of the chair and running off. As Ruk pursues him, Chapel yells after him, "I order you not to harm him!" Ruk imitates Chapel's voice in an attempt to lure Kirk out of hiding, but Kirk sees through the ruse and attacks Ruk with a broken-off stalactite. In the struggle, Kirk falls and hangs dangerously from the edge of another seemingly bottomless cavern.

Act Four[]

But after Ruk stares at Kirk for a moment as he dangles off the precipice, the giant android pulls Kirk to safety, perhaps in obedience to Chapel's order not to harm the captain.

Meanwhile, on the Enterprise, Spock is surprised by Kirk's unannounced return, as he casually strolls past him in a corridor. When Spock enters Kirk's quarters and tries to inquire about Dr. Korby, Kirk snaps at him, "Mind your own business, Mr. Spock. I'm sick of your half-breed interference, do you hear?" Immediately after this uncharacteristic outburst, Kirk is pleasant again; he returns to the planet, leaving a very bewildered Spock behind. Realizing that something is wrong, he forms a security team to prepare to beam down after "Kirk" has left the ship.

Back on the planet, the real Kirk asks Andrea to kiss him. He hopes to confuse and scramble her programming by showing her what kissing really is. She gives him the same type of kiss she gave him earlier: a brief, gentle kiss on the lips. After the brief kiss, she half raises her left arm ready to slap him – another repetition from the previous kiss. Kirk stops her from slapping him, grabs her, pulls her in close, and gives her a much longer, much more passionate French kiss. This confuses her, since she was not programmed to respond to him. Deep down, she enjoyed it, but her circuitry protested.

Andrea leaves and Kirk is then confronted by Ruk; Kirk discusses the Old Ones with Ruk. Kirk learns more about the ancient civilization: they built their machines too well, became fearful of them, and started shutting them off. But survival outweighed programming, and the androids murdered their creators. Goaded by Kirk, Ruk grows angry and realizes that Korby is doing exactly the same thing. He starts to threaten Korby, who is forced to destroy Ruk with a phaser. Meanwhile, Andrea comes across the android Kirk and tries to repeat the romantic advances, thinking he is the real Kirk. When the android Kirk refuses, citing it as "illogical," Andrea vaporizes him with a phaser.

In a scuffle between Kirk and Korby, a section of skin is torn from the back of Korby's left hand when he catches it in a sliding door – revealing wires and circuits. Chapel sees to her horror that Korby is an android as well.

Korby android exposed hand

Korby's hand exposed

Korby tries to explain to a shocked Chapel that while critically injured, he built a perfect body and decanted himself into it. He claims that he's still the real Roger Korby, but is unable to demonstrate any uniquely "Human" qualities.

The breakdown of this small segment of android civilization reveals the pitfalls of Korby's utopian vision. Soon enough, even he realizes this, and hands over his phaser in defeat and despair. But Andrea will not relinquish hers, and she confusedly tries to profess her love for Korby. As she kisses him, Korby pulls the trigger of the laser pistol in her hand, destroying them both.

Spock and his three-man security team arrive and come upon Kirk and Chapel. When Spock inquires about Korby's whereabouts, Kirk replies truthfully to his first officer, "Dr. Korby… was never here."

Back on the ship, Chapel decides to stay on the Enterprise. Spock then tells Kirk of his dismay over his use of the term "half-breed". Kirk replies, "I'll remember that, Mr. Spock… the next time I find myself in a similar situation."

The Enterprise leaves Exo III's orbit and travels on through space.

Log entries[]

Memorable quotes[]

"Dr. Korby has discovered that as their sun dimmed, the inhabitants of this planet moved underground, from an open environment to this dark world. When you were a student of his, Christine, you must have often heard Dr. Korby remark how freedom of movement and choice produced the Human spirit. The culture of Exo III proved his theory. When they moved from light to darkness, they replaced freedom with a mechanistic culture."

- Dr. Brown, describing the cultural changes which took place on Exo III to Kirk and Chapel

"You think I could love a machine?"
"Did you?"

- Korby and Chapel, on Andrea

"A thing is not a woman."

- Korby, to Chapel

"This is how you make an android."

- Korby

"Andrea, kiss Captain Kirk." [Andrea kisses him] "Now, strike him." [Andrea strikes him]

- Roger Korby

"Choose, Christine. Which is your captain?"
"I don't know. They're exact. I honestly don't know."

- Korby and Chapel, when Kirk is duplicated as an android

"Mind your own business, Mister Spock. I'm sick of your half-breed interference! Do you hear?"

- Kirk, implanting a mental suggestion into his android duplicate

"Eating is a pleasure, sir. Unfortunately, one you will never know."
"Perhaps. But I will never starve, sir."

- Kirk and his duplicate

"In android form, a Human being can have practical immortality. Can you see what I'm offering mankind?"
"Programming – different word, but the same old promises made by Genghis Khan, Julius Caesar, Hitler…"
"Can you imagine how life could be improved if we could do away with jealousy, greed, hate?"
"It can also be improved by eliminating love, tenderness, sentiment. The other side of the coin, doctor."

- Korby and Kirk

"Oh, no…No…Not programmed for you."

- Andrea, confused after sharing a long passionate kiss with Kirk

"That was the equation! Existence! Survival must cancel out programming!"

- Ruk, before Korby destroys him

"Aren't you doing exactly what you hate most in Humans: killing with no more concern than when you turn off a light?"
"I am not a computer. Test me. Ask me to solve any… Equate… Transmit… Christine! Christine, let me prove myself!…"
"Don't you see Roger? Everything you've done has proved it isn't you."
"I AM Roger Korby!"

- Kirk, Korby, and Chapel, after Korby's true identity is revealed

"Doctor Korby… was never here."

- Kirk, to Spock

"Frankly, I was rather dismayed by your use of the term 'half-breed', Captain. You must admit it is an unsophisticated expression."
"I'll remember that, Mr. Spock… the next time I find myself in a similar situation."

- Spock and Kirk

Background information[]

Production timeline[]


  • The first draft of this episode's script was completed 26 June 1966. The revised final draft was turned in 27 July.
  • This was the first episode to be repeated by NBC on 22 December 1966. [1]
  • The script of this episode was in such a bad shape, that Gene Roddenberry had to make revisions simultaneously with the filming of the episode, and shooting had to wait until new pages arrived. (Inside Star Trek: The Real Story, p. 204)
  • James Goldstone, who directed the second pilot, "Where No Man Has Gone Before" was hired to direct this episode, because the production staff greatly praised his work. However, filming of this episode went two days over schedule (mostly due to the aforementioned script problems), resulting in eight shooting days. Goldstone was never re-hired. (Inside Star Trek: The Real Story, p. 204)
  • The closeup insert shot of Korby's hand reaching for his phaser and pulling the trigger, killing both him and Andrea, was filmed in post-production on 13 September 1966. Frank da Vinci served as Korby's hand double, while Jeannie Malone stood in for Andrea. (These Are the Voyages: TOS Season One [page number?edit])
  • While much of the score in this episode is stock music, small bits of new music were composed for it by Fred Steiner. Andrea's theme was re-used in "This Side of Paradise" as Leila Kalomi sought to explain the nature of the Omicron Ceti III spores to Spock, while the Ruk music signified danger in many future episodes.
  • In 1998, the Sci-Fi Channel aired all the original Star Trek series episodes in their complete, non-syndicated format, with added interviews from some of the series stars, guest stars and production people, called "Star Trek Insights". Sherry Jackson said in her interview regarding the scene when Kirk kisses Andrea, "I must say when he kissed me on screen, he really kissed me!" In the same interview Jackson said that William Shatner's chest had to be shaved for his nude scenes in the android machine. [2].
  • The reference book Star Trek: The Original Series 365 (p. 066) speculates that the character of Andrea may be closely related to the title of the episode she appeared in, "What Are Little Girls Made Of?". The book makes this connection due not only to the fact she is "indeed" a girl, albeit a girl android, but also because "one has to assume that all of the 'everything nice' ingredients went into creating her," a reference to "What Are Little Boys Made Of?", a nursery rhyme which provided the episode title.
  • During the syndication run of Star Trek, no syndication cuts were made to this episode, with the exception of the scene in the Transporter Room with Kirk and Chapel beaming down.


Sets and props[]


  • In the still photograph of Korby on Spock's station video screen, he is wearing one of the turtleneck shirts from the two pilots.
  • Andrea's dress was designed by TOS Costume Designer William Ware Theiss. He evidently designed it to accent the natural contours of her body. (The Star Trek Compendium, 4th ed., p. 41) Star Trek: The Original Series 365 (p. 069) suggests that this costume might have been inspired by the work of designer Rudi Gernreich, particularly the monokini.
  • To test the effectiveness of Cassidy's Ruk costume and makeup, the producers arranged for Cassidy to receive a visiting clothes dealer while costumed as Ruk. Sure enough, the salesman, who thought he was calling on Gene Roddenberry, was so frightened at Cassidy's intimidating character, he was barely coherent even as he attempted to do his pitch. However, the salesman eventually recovered, and Roddenberry ended up purchasing some pants from him. (The Making of Star Trek, 7th ed., pp. 352-353)


  • This episode marks the final appearance of the early black and white phaser 2. It was replaced by more detailed blue-gray and black models.
  • A key point of the Saturday Night Live spoof of Star Trek conventions, featuring William Shatner, was the question from a fan about the combination of Kirk's safe. The combination is different in this episode than in "This Side of Paradise", "The Tholian Web", and "Turnabout Intruder".
  • This episode marks the first redshirt deaths in the series, starting with Crewman Mathews.
  • When Spock asks Chapel if she recognizes Korby's voice, she asks him if he's ever been engaged. He does not answer her. Spock would later reveal in "Amok Time" his relationship with T'Pring as "less than a marriage but more than a betrothal".
  • When Kirk and the Android Kirk are discussing Kirk's brother Sam, it is said that Sam has three sons. In the episode "Operation -- Annihilate!", one of these sons, Peter, is encountered.


  • Robert H. Justman personally assembled the episode previews for the series, some of which had specially-recorded narration by William Shatner, as this episode does. (citation needededit)
  • The preview contains a Captain's Log recorded solely for the preview: "Captain's log, stardate 2712.4. Planet Exo III. Dr. Roger Korby has been located. And I have become a prisoner in his underground world."
  • A different take from that in the final episode of Ruk using the communicator to speak with Spock is shown, and some of Kirk’s dialogue as mimicked by Ruk has been edited and rearranged to shorten it slightly.


  • This episode produced a sequel in the form of the novel Double, Double by Michael Jan Friedman. In it, another Brown android returns from an expedition, finds Korby and the others "dead," and creates a new Kirk android. The androids then again attempt to put Korby's plan into operation, taking over the Enterprise and Hood while arranging the removal of the original Kirk.
  • According to the novella "The Worst of Both Worlds", the mirror universe James T. Kirk of the ISS Enterprise destroyed the last surviving member of the android society (presumably Ruk's mirror counterpart) on Exo III, who had likewise turned on their masters and killed them.

Video and DVD releases[]

Links and references[]


Also starring[]

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Uncredited co-stars[]

Stunt doubles[]



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