The Changeling (episode)
The Enterprise finds an ancient interstellar probe from Earth, missing for 265 years, which has somehow mutated into a powerful and intelligent machine sterilizing entire populations that do not meet its standards of perfection.

Summary

Teaser
The  is en route to the Malurian star system, investigating a distress call. Lieutenant Uhura has received no response to hails on any frequency, even after Captain Kirk reminds her of a Federation science team transmitter from Doctor Manway. However, Spock's sensor data contains tragic news: although there should be over four billion Malurians there are absolutely no readings of life anywhere in the system. As Kirk and Spock speculate about what could have caused the eradication of life in such a short time, a large bolt of energy comes out of nowhere. Kirk orders red alert, and the object violently impacts upon the Enterprises shields.

Act One
The entire crew is hurled around, and when things stabilize, Kirk orders Uhura to inform Starfleet of the apparent disappearance and the attack. Spock reports that the shields will stand only three more such impacts, as they have been reduced by 20%. The Enterprises shields continue to be battered by repeated attacks. Finally, after the shields are completely gone and a photon torpedo in response has been completely absorbed, Kirk orders Uhura to hail the very small object Spock has identified as the source of attack. The object stops its assault and tries to respond to the hail with an old-style binary code. The crew has some difficulty translating, but eventually succeeds. The object identifies itself as Nomad, and its mission as "non-hostile." 

As it is only a fraction over one meter in length Kirk has it beamed aboard, if only to prevent it from firing on the ship again. It introduces itself and Kirk remembers the launch of a probe named Nomad in the early 2000s, and Spock says it was reported destroyed with no more in the series. 

Later it is revealed that the object had stopped its assault when it heard Kirk's name, somehow believing that Kirk is its creator.

Act Two

Nomad wastes no time investigating the ship, with only Kirk's orders preventing it from having free rein. Knowing how powerful it is, and that it stated it was programmed to destroy "biological infestation," Kirk orders two security guards to watch it at all times, but Nomad is able to evade them. Furthermore, it seems highly logically-minded and gets confused whenever it encounters something illogical; when it hears Uhura singing "Beyond Antares" on the bridge from the auxiliary control room, it leaves Lieutenant , who was watching it, and goes to investigate. 

Meanwhile, Kirk and Spock check the computer on Nomads creation and launch. Originally, Nomad was built by Jackson Roykirk for a deep-space extraterrestrial contact mission early in the 21st century, in the year 2002, but was lost in a meteor shower, where it was presumed destroyed. Somehow, it got a directive to kill, and must have killed the Malurians.

Nomad arrives on the bridge to question Uhura about the song. She attempts to explain it, but Nomad does not understand what music is. Nomad tries "probing" Uhura's mind to find the information, and wipes her memory in the process. Scott sees this and attempts to save Uhura from the probe, but Nomad retaliates violently. A blast of energy throws Scott aside, and he crashes to the floor near the viewscreen. Upon Dr. McCoy's examination of Scott, he declares him dead, to Kirk's shock.

Act Three
Just after Scott's death, Nomad announces to Kirk if he wishes to have the Enterprises chief engineer "repaired". Kirk immediately replies in the affirmative, although McCoy tells him that Scott must be revived soon. Spock has detailed files on Human physiology brought up at his station, which Nomad scans. McCoy then leads Nomad to sickbay, where the probe instantly revives Scott, who is baffled as to why everyone is looking down at him on a bio-bed. Kirk also orders Nomad to help Uhura, but Nomad says it is not possible. McCoy and Nurse Chapel proceed to re-educate her using the computer.

This event proves disconcerting to Kirk, who then orders Nomad to be guarded and analyzed by Spock. After the analysis and a background check on Nomad in the ship's data banks, Spock gets enough details through a mind meld with the probe to fill in the blanks. After the meteor collision, Nomad was disoriented and wandered through space until coming into contact with Tan Ru, an alien probe whose mission was to collect and sterilize soil samples, presumably as a prelude to colonization. The two melded into this new Nomad, combining their technology and missions into one extremely powerful probe bent on sterilizing any imperfect lifeforms it encountered, using its own perceptions of perfection (i.e. itself) as a measuring stick. As such, it destroyed all life in the Malurian star system but because its original programming was damaged and corrupted in the merger, it erroneously equates Kirk with its creator, not realizing that the two are different people and its creator has been, in fact, dead for centuries.

While Kirk and Spock are gone, Nomad leaves the confined area, killing two security officers in the process, and decides to improve the efficiency of engineering, taking the Enterprise eventually to warp 10 in the process. Kirk arrives and forces it to stop. Unfortunately, the mind meld and an unintentional admission from Kirk confirm to Nomad that its creator is an imperfect biological entity, and with that knowledge, it leaves on Kirk's order to contemplate the new data with two security officers. They deduce it will not obey for long and will eventually sterilize Earth.

Act Four
En route, Nomad escapes, killing the two guards, and goes to sickbay to scan Kirk's personnel file. McCoy finds Nurse Chapel has been attacked and signals Kirk and Spock to come to sickbay. They realize Nomad is gathering the information they feared. Furthermore, Scott informs them from the bridge that Nomad has turned off all life support on the ship. 

With little time left, Kirk comes to recognize Nomads refabricated mission and takes a gamble to confront it again before it returns to Earth to "sterilize" the planet's population. Through questioning Nomad on its prime directive in engineering, Kirk confirms his suspicion that it must execute it with no exceptions, and then reveals that he indeed is not Nomads creator. He explains that Nomad had mistaken him for Roykirk who is long dead, the two men's names being similar, and as such Nomad has committed an error; furthermore, it has compounded that error with two more, specifically failing to realize its mistake and failing to immediately execute its prime directive as a result. This causes Nomad to lock up in an irreversible logic loop, its stubborn belief that it is perfect conflicting with the realization that it is in error. Capitalizing on the weakened Nomad, Spock and Kirk manage to get it to the transporter room with anti-gravs and have Scott beam it out into space just as it executes its prime function on itself. The explosion is detected near the Enterprise and Nomad is no more.

Later, on the bridge, Spock commends Kirk on his dazzling display of logic that allowed them to defeat Nomad. McCoy enters through the turbolift and reports that Uhura is now reading at a college level and should be able to return to duty within the week. Spock laments the loss of Nomad, noting that it was a "remarkable instrument." Kirk jokingly wonders what Spock is so upset about, given that the machine considered Kirk to be its "mother". "You saw what it did for Scott. What a doctor it would have made. My son, the doctor. Kind of gets you right here, doesn't it?" Kirk says while pointing to his heart.

Log entries
 Captain's log, USS Enterprise (NCC-1701), 2267

Memorable quotes
"This is one of your units, creator?" 
"Yes, he is."  
"It functions irrationally."
- Nomad and Kirk, on the "unit" McCoy

"My function is to probe for biological infestations, to destroy that which is not perfect. I am Nomad."
- Nomad, explaining its directive

"It would seem that Nomad is now seeking out perfect life-forms, perfection being measured by its own relentless logic."
"If what you say is true, then we have taken aboard our vessel a device which sooner or later must destroy us."
- Spock and Kirk, realizing the danger Nomad poses to them

"That unit is a woman."
"A mass of conflicting impulses."
- Spock and Nomad, on the "unit" Uhura

"Does the creator wish me to repair the unit?"
- Nomad, asking Kirk if he should "repair" Scott

"A man is not just a biological unit that you can patch together."
- McCoy, after Nomad heals Scott

"This unit is different. It is well-ordered."
 - Nomad, on the "unit" Spock

"The creation of perfection is no error."
- Nomad, refuting Kirk's claim that its creation was an error

"You are the Creator."
"You're wrong!  Jackson Roykirk, your creator, is dead!  You have mistaken me for him, you are in error!  You did not discover your mistake, you have made two errors. You are flawed and imperfect. And you have not corrected by sterilization, you have made three errors!"
- Nomad, sent into a logic feedback loop by Kirk

"My congratulations, captain. A dazzling display of logic."
"You didn't think I had it in me, did you, Spock?"
"No, sir."
- Spock and Kirk, on Nomads induced self-destruction by Kirk

"It's not easy to lose a bright and promising son… my son – the doctor."
- Kirk, whose "son – the doctor" brought Scott back to life, about Nomad

Background information

Production timeline
Story outline by John Meredyth Lucas: 
Revised story outline: 
First draft teleplay: 
Second draft teleplay: late-
Staff rewrite: 
Final draft teleplay by D.C. Fontana: 
Revised final draft by Gene L. Coon: 
Additional page revisions: , , 
 Filmed:  – 
Day 1 – , Thursday – Desilu Stage 9: Int. Bridge
Day 2 – , Friday – Desilu Stage 9: Int. Bridge
Day 3 – , Monday – Desilu Stage 9: Int. Transporter room, Auxiliary control center
Day 4 – , Tuesday – Desilu Stage 9: Int. Engineering, Corridors
Day 5 – , Wednesday – Desilu Stage 9: Int. Sickbay
Day 6 – , Thursday – Desilu Stage 9: Int. Brig, Briefing room
Day 7 – , Friday (Half Day) – Desilu Stage 9: Int. Briefing room
Additional filming (Pickup shots) – , Friday – Desilu Stage 9
Original airdate: 
Rerun airdate: 
First UK airdate: 
Although never credited, this episode – which depicted an Earth-launched space probe that acquires almost unimaginable powers in the course of the search for its "Creator" – became the inspiration behind the first Star Trek film. (It also inspired "The Questor Tapes", a 1974 series pilot written by Gene Roddenberry and Gene L. Coon which also featured a robot with a damaged memory who searched for its creator.) For this reason, some fans have appended to  the pun subtitle "Where Nomad Has Gone Before." (Star Trek: The Original Series 365, p. 188)

Cast and Characters

 Director Marc Daniels portrays Jackson Roykirk in the photograph, wearing Scott's dress uniform.
 Eddie Paskey is seen in a gold shirt in this episode so he would match the standard stock footage screen shot with George Takei and an extra's left shoulder. In  he is seen wearing gold in the corridor during Kirk-to-crew announcements (the same shot was recycled in many episodes, including  and ). Paskey also appears in a red technician's jumpsuit in the main engineering scenes.
Lemli's first name, Roger, is given in this episode. His last name wasn't revealed until the following season, in .
In conventions, Nichelle Nichols frequently tells a story of getting into a dispute with director Marc Daniels over the filming of this episode. As it had already been established that Uhura's first language was Swahili, Nichols believed that, after her mind was erased, Uhura would revert to her first language. However, as Nichols herself did not speak Swahili, Daniels wanted Uhura to just speak English. Nichols refused to, telling Daniels, "Nichelle Nichols doesn't speak Swahili, but Uhura does!"  Gene Roddenberry was eventually brought in to settle the dispute, and he sided with Nichols. A linguist specializing in Swahili was then brought in to write the few lines of Swahili that are spoken in the episode.
By the time of her next appearance () Uhura has apparently regained all of her faculties. It is possible that Nomad did not fully erase her memories, merely "locked" them away, and it was possible with time for her to retrieve them.
 After Nomad explodes, William Shatner quickly raises his hand to the camera as the scene fades away. An outtake of this scene is incorporated into the blooper reel of the show's second season: At one point, Shatner turns to the camera and declares, "Listen, about that bacon – no, really!" and then appears to swallow something, presumably medication for an upset stomach. His comment follows an earlier outtake that shows him sitting in the captain's chair on the bridge and confiding, "No, listen, that bacon is really bad… it just stays with you all day."
 Also in the blooper reel: When Shatner tells Nomad that the Enterprise is prepared to beam it aboard, James Doohan says, "But captain – you forgot all about the environment and all that stuff. Do you want to really do that?" A grinning Doohan steps out of camera frame, leaving a slightly perplexed Shatner behind, bemusedly shaking his head. Doohan did not deliberately ruin the take, however. It was already ruined since Shatner actually did forget to say the dialogue concerning the environment.

Continuity
William Blackburn appears in three different uniform colors in this episode: his usual gold (as Hadley), a blue uniform in a corridor scene, and in a red technician's jumpsuit in main engineering.
Footage of Nomad exiting the turbolift is recycled to show him leaving sickbay.
When the two security guards shoot Nomad for not obeying them, the visual effects artists apparently used the door frame behind the guards as a guideline for the boundary of Nomads shields. This has the unfortunate effect of making it seem as if the guards' phaser beams are striking the door frame.
Spock mentions that Nomads first attack on the Enterprise was the equivalent of ninety photon torpedoes. Surprisingly, this attack only reduced the shields by 20%. This seems even stranger a few moments later, when Nomad absorbs the energy of a single photon torpedo and Kirk wonders how anything could "absorb so much energy – and survive".
Surprisingly, too, Uhura is re-educated within a matter of days, presumably with all her memories intact as well. Possibly her memories were not really erased, but overwritten, just as a computer file may have its FAT entry overwritten but can easily be recovered. Exabytes of data would take a while to restore but would not take nearly as long as learning from a zero start-point.
 This episode marks one of four times Kirk is able to "talk a computer to death". This technique is also used in , , and , and was similarly done to a robot in 
Even though this episode is stated to take place on stardate 3541.9, the episode list from the official website says it takes place on stardate 3451.9.

Video and DVD releases
RCA CED Videodisc with Space Seed 1981
UK VHS release (CIC-Arena Video): catalog number VHL 2057, 
This release included  and was originally unrated, as it was released prior to the . After , it received a rating of PG.
Original US Betamax release: 
UK VHS release (two-episode tapes, CIC Video): Volume 20, catalog number VHR 2353, release date unknown
US VHS release: 
UK re-release (three-episode tapes, CIC Video): Volume 2.3, 
Original US DVD release (single-disc): Volume 19, 
As part of the TOS Season 2 DVD collection

Apocrypha
Tokyopop's Star Trek: The Manga: Kakan ni Shinkou had a story titled "Communications Breakdown", set after the episode. The story starts with a captain's log mentioning that it's been twelve days since the encounter with Nomad.

Links and references

Starring 
William Shatner as Capt. Kirk

Also starring
Leonard Nimoy as Mr. Spock
DeForest Kelley as Dr. McCoy

Featuring 
James Doohan as Scott
Nichelle Nichols as Uhura
George Takei as Sulu
Majel Barrett as Christine Chapel

With
Blaisdel Makee as 
Barbara Gates as Crewwoman
 Meade Martin as Crewman
Arnold Lessing as Security Guard
And
Vic Perrin as Nomads voice

Uncredited co-stars
William Blackburn as Hadley
Frank da Vinci as
Brent
Vinci
Marc Daniels as Jackson Roykirk (photo)
Roger Holloway as Roger Lemli
Jeannie Malone as a Yeoman
Eddie Paskey as Leslie
Frieda Rentie as a Lieutenant
Unknown actors as
 Security Guard 1
Security Guard 2 and 3
Transporter assistant

Stunt double
Jay Jones as stunt double for James Doohan

Stand-ins
William Blackburn as stand-in for DeForest Kelley
Frank da Vinci as stand-in for Leonard Nimoy
Roger Holloway as stand-in for James Doohan
Eddie Paskey as stand-in for William Shatner

References
2000s; 2002; accident; alien; analysis; analysis sector; anatomy; anger; answer; ; antigrav; antimatter input valve; aptitude; area; attack; atmosphere (aka air); audio; auxiliary control room; baby; background radiation; ball; bearing; "Beyond Antares"; billion; binary; biological function; biological unit (aka "unit"); blue; body; "Bones"; brain; brain damage; brig (aka security cell); census; central nervous system; chance; ; channel 1; Chart 14A; chief engineer; child; choice; circuit; college; collision; colonization; communication channel; computer; condition red; contact; cooperation; coordinates; Creator; creature; cylindrical; damage; damper; danger; ; deep space; ; disease organism; distress call; ; dog; dream; Earth; educational tape; effect; efficiency; emotion; emptiness; energy; energy release control; English language; environment; ; evasive maneuvers; fact; fairy; Federation; Federation science team; feeling; first grade; flash feed; flaw; force field; force field door; formula; frequency; guard; hailing frequency; harm; heart; ; history computer; Human; hyperencephalogram; hypothesis; impulse power; information; instruction; intelligence; interfactor; interplanetary code; interplanetary war; interstellar probe; kilogram (aka kilo); kilometer; knowledge; knowledge bank; language equivalence; Latin language; launch point; lecture; legend; length; library; lifeform; life support system; location; log; logic; long range sensor sweep; love; Luna; machine; main computer; maintenance crew C5; ; Malurians; Malurian population; Malurian system; manual control; manual override; Manway; mathematics; matter-antimatter propulsion system; mechanism; medical history; memory bank; meter; meteor; Milky Way Galaxy; Mind meld; minute; miracle; mission; mistake; mother; music; name; natural satellite; neurology; Nomad; non sequitur; opinion; overload; parasitical beings; path; percent; perfection; personnel file; phaser bank; photon torpedo; physical; physiology; point of origin; point of reference; polymass; population; private transmitter; probe; problem; programming; programming tape; protective screen; prototype; question; radioactive residue; range; reader; reading; rebirth; red alert; repair crew (aka maintenance crew); risk; routine report; Scots language; science team; scientist; screens; search; security team; sensor; sensor range; series; shape; shielding power; ship's translator; shock; signal; singing; soil; soil sample; Sol; Sol system; son; space; spacecraft; space happy; speech; speed; "stand by"; star; star chart; Starfleet Academy; Starfleet code; Starfleet Command; stress (physics); ; sterilization procedure; structural integrity; stubbornness; Swahili language; Symbalene blood burn; symbol; Tan Ru; tape; telepathy; thing; thinking machine; thousand; translator computer; transmission speed; Vulcan mind probe; warp engine power; warp factor; warp maneuvering power; warp power; warp power indicator; week; weight; woman; working order

Library computer references
Nomad schematic: acquisition sensor; coupler prediction scanner; data assimilation digital encoder; International Designator; magnetohydodynamic vernier-pulse; regenerative mode emulsifier; selective amplifier screen; sperographic analysis computer; tracking screen; transmission

Chart 14A locations: Jupiter; Mars; ; Neptune; Pluto; Saturn; Uranus; Venus

External links

de:Ich heiße Nomad
es:The Changeling
fr:The Changeling (épisode)
it:La sfida (episodio)
ja:超小型宇宙船ノーマッドの謎（エピソード）
nl:The Changeling
pl:The Changeling

TOS episodes