Star Trek (1967): S02E03 – The Changeling


“The Changeling” is the third episode of the second season of the American science fiction television series Star Trek.

Written by John Meredyth Lucas and directed by Marc Daniels, it was first broadcast on 29 September 1967.

The crew of the USS Enterprise deals with a life-destroying space probe originally launched from Earth. The plot contains similarities to the later 1979 Star Trek film.


The Enterprise investigates a distress call from the Malurian star system. Upon arrival, First Officer Spock reports no life readings from any of the 4 billion inhabitants, despite otherwise normal recent communications. The ship’s shields are suddenly activated when a meter-long cylindrical object attacks with a powerful energy bolt equivalent to 90 photon torpedoes. Captain Kirk orders return fire, but his weapon’s energy is simply absorbed by the object. Following several more incoming attacks, and on the verge of his ship’s destruction, Kirk hails the object. After several back-and-forth attempts, the object requests in-person communication with the Captain and allows itself to be beamed aboard the ship.

The object identifies itself as “Nomad”, and refers to Captain Kirk as “the Creator”. Spock reports that a Nomad space probe was launched from Earth during the early 21st Century; its mission was to explore the galaxy and seek out new life, but it had been reported destroyed – a report that Spock acknowledges may have been wrong. The current Nomad has mistaken Kirk for Dr. Jackson Roykirk, the scientist who created and programmed the original probe. Nomad’s new mission is to seek out and eliminate any “biological infestation” that it deems imperfect, including the entire population of the Malurian star system. Nomad states that its attempt to destroy the Enterprise had not been necessary since “the Creator” was aboard.

Left in the care of a crew member, Nomad escapes to investigate the sound of Lieutenant Uhura singing, which it detects over the intercom. Arriving on the bridge to make inquiries, it asks Uhura to “think about music” while probing her mind, which erases her memory. When Chief Engineer Scott tries to intervene, Nomad kills him, pleading self-defence. Upon learning that Kirk cannot repair Scott, Nomad offers to restore him to life. Nomad heals Scott, but cannot “repair” Uhura’s memory loss; Nomad is taken to the brig.

To uncover more information, Spock performs a Vulcan mind meld with the machine. He discovers that Nomad collided with a meteor and was severely damaged. It then wandered through space, finally coming into contact and merging with a powerful alien probe called Tan Ru, designed to obtain and sterilise soil samples from other planets. Nomad partially integrated Tan Ru’s agricultural mission directives, interpreting them to mean “sterilise imperfections”. The merging of the two probes imbued Nomad with Tan Ru’s vast powers, sufficient to destroy life throughout an entire solar system. Kirk compares Nomad’s reincarnation to the changeling legend, in which a human child is switched with a fairy child, with the latter assuming the identity of the former.

Nomad escapes from its cell, killing two guards who attempt to stop it. The probe makes its way to the engineering deck, where it begins to make adjustments to the engines, accelerating the ship beyond its normal maximum warp speed. As Kirk arrives, Nomad tells him that engine efficiency has been boosted 57%; Kirk orders it to reverse the changes since other structures on the Enterprise cannot handle the faster speed. Nomad complies.

Exasperated by Nomad’s prejudice toward imperfect “biological units”, Kirk points out that its own “Creator” is a biological unit. Nomad responds that it must “reevaluate.” Kirk orders the probe back to the brig, and it departs under security guard. Spock then suggests to Kirk that admitting to Nomad that he, “the Creator,” is imperfect was probably a mistake. Spock also observes that because Nomad has threatened to return to its “launch point,” the Earth and all its inhabitants are now at risk of sterilisation.

En route to the brig, Nomad kills its two security escorts and heads instead to sickbay. After examining Kirk’s medical files and verifying his imperfections as a biological unit, Nomad’s “reevaluation” is complete. It proceeds to engineering, incapacitates crew members and shuts down the ship’s life-support systems, thus rendering the Enterprise habitable for only a short time longer.

Kirk arrives and again confronts the probe, questioning it about its mission. When Nomad declares that its directive to sterilise imperfections allows no exceptions, Kirk points out that Nomad itself is imperfect, since it has mistaken Captain Kirk for its true creator Roykirk. He then claims that Nomad has committed two other errors, by not discovering its own mistake, and by not sterilising itself as imperfect. Nomad begins to analyse the implications of Kirk’s claims, a process that causes noticeable stress to its systems. Kirk and Spock carry Nomad in a rush to the transporter room and, with a final command from Kirk to “exercise your prime function,” beam it into deep space. Seconds after transport, an explosion is detected near the Enterprise and Nomad is no more. The episode ends on a humorous note, with Kirk observing that he is proud that his “son” Nomad, having healed Mr. Scott, would have made a good doctor.

Star Trek TV Series

You can find a full index of Star Trek TV series here.

Star Trek TV Series, Films, and Documentaries

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Production & Filming Details

  • Director(s): Marc Daniels.
  • Writer(s): John Meredyth Lucas.
  • Production: Desilu Productions (1966-1967) and Paramount Television (1968-1969).
  • Distributor(s): Paramount Pictures (1966-2006), CBS Paramount Television (2006-2007), and CBS Television Distribution (2007-Present).
  • Original Network: NBC.
  • Release Date: 29 September 1967.
  • Running Time: 50 minutes.
  • Country: US.
  • Language: English.

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