(written from a Production point of view)
At the planetoid Memory Alpha, an Enterprise crew member's body is taken over by mysterious energy lifeforms.
While the USS Enterprise ferries Lieutenant Mira Romaine to Memory Alpha, a planetoid that serves as the central library of the Federation, Montgomery Scott and Romaine spend a good deal of time together working in engineering and Scott seems to be falling in love with her.
On the bridge, Spock detects an apparent storm from his station, approaching the ship at warp factor 2.6, and concludes that it cannot be a natural phenomenon. After Kirk orders yellow alert, the storm bypasses the shields and penetrates the Enterprise. Soon after, the crew loses their voice.
The phenomenon backs off, and the crew is normal again. Romaine, however, faints after making some strange inaudible sounds, and is taken to sickbay. Dr. McCoy examines the lieutenant, but Romaine minimizes the event to the point of being uncooperative. Dr. McCoy insists that Romaine was the most affected of the crew of 430 and he wants to know why. Scott attributes it being her first deep space mission, and coaxes Romaine to cooperate more fully but Romaine fears her assignment is at risk.
Lieutenant Sulu projects the storm's course as heading for Memory Alpha, which was built without defensive shields in view of its academic purpose. The Enterprise cannot contact Memory Alpha to warn it, nor reach Memory Alpha until the storm has come and gone.
Kirk assembles a landing party. Upon beaming over to Memory Alpha, they learn the generator is inoperative and all the staff are dead.
The landing party finds one person alive – a female who is making the same garbled sounds Romaine made during the initial "attack" on the bridge. She soon dies, of "severe brain hemorrhaging due to distortion of all neural systems, dissolution of autonomic nervous system", according to McCoy. The other Memory Alpha personnel have each had a different brain center destroyed.
Kirk asks Sulu to have Romaine beamed down for questioning. Romaine, however, interrupts the dialogue, seeing that the staff is dead, to urge the crew to get back to the Enterprise, as she is sure the storm is returning. When Sulu soon reports the same thing, Kirk orders the landing party back to the ship. Lieutenant Kyle has a tough time trying to complete the transport of Romaine, though, as it is interfered with but eventually completed by Scott.
Romaine tells Scott she saw the dead workers on Memory Alpha, "in their exact positions." Scott ascribes it simply to "space" and tells Romaine not to report it unless "you want to spend the rest of the trip in sickbay."
As the storm closes in on the Enterprise, Ensign Chekov cannot evade it. Spock reports ten distinct lifeforms in the cloud and doubts that the ship can adequately be shielded against it. The cloud approaches the ship. Since Spock has reported that the entity may be alive, Kirk believes he can reason with it through communication. He has Uhura open hailing frequencies and tie in the universal translator. He announces that the crew of the Enterprise mean it no harm and asks that the "storm" cease its approach as physical contact with their form of life is fatal. The cloud passes the Enterprise's starboard side and positions itself directly in front of the ship.
It is increasing its approach. Kirk says that "perhaps it understands another kind of language." He orders the ship be put on red alert and for phasers to be fired, first a warning shot, then a shot directly into the cloud. As Sulu reports that the direct shot has slowed the cloud, Kirk orders phaser crews to fire again. In engineering, Romaine has become affected by the phenomenon again in agony, comforted by Scott. Scott reports by intercom that the damage to the cloud seems to be killing Romaine as well, so Kirk calls off the attack.
Kirk orders key personnel to the briefing room. There, Kirk searches for personal data on Romaine from Starfleet that might relate to the attacking cloud. McCoy reports that two hyperencephalograms show that Romaine's brain wave patterns have been altered since the encounter. Spock thinks McCoy has presented the wrong tape, but his concern shows that the hyperencephalogram now matches the ship's tracking of the cloud. Her mind is joining that of the attacker. Scott now discloses that Romaine has been seeing future events. Kirk asks Romaine to describe each event. She describes the effects that have occurred, and one that has not occurred: Scott dying.
Sulu reports from the bridge that attempting to escape at warp factor 8 is useless. Kirk asks Romaine not to resist but to let the aliens operate through her, hoping to control that moment to save the ship. Finally, he orders the medical lab to prepare antigrav units. As they make their way to the lab, the lights appear in a corridor, heading toward Romaine.
The lights swarm on Romaine and enter her body. Scott despairs that Romaine is lost, and McCoy believes there is no way to force the lights out without killing her. Romaine is determined to retain her identity, but begins speaking for the aliens, which Spock encourages.
The alien reports through Romaine that they are from Zetar, a planet where all humanoid life was destroyed. They are the will of the last hundred from Zetar, who have searched for a millennium "for one through whom we can see and speak and hear and live out our lives."
Kirk insists that Romaine's body "has its own life to lead." The aliens say they regret the killing they have done, but intend to survive. Scott insists to Kirk that Romaine cannot hurt him and carries her to the pressure chamber. The aliens attack Scott – as Romaine foresaw – but the attack is ultimately not fatal. Chamber pressure is increased, despite the risk of killing Romaine. The aliens are successfully driven out of her body. "Now, we have all the time in the world," Scott beams.
The Zetarians did not further attack the Enterprise. In sickbay, Kirk asks McCoy and Spock for estimates on the incident's long-term impact on her. Spock thinks the episode should strengthen her. Kirk orders a return to Memory Alpha to let Romaine begin her assignment. Kirk believes they may have an "Enterprise first," with Scott, McCoy, and Spock, for once, in complete agreement. Kirk laughs at this.
"I didn't think Mister Scott would go for the brainy type."
"I don't think he's even noticed she has a brain."
- - Chekov and Sulu, on Scott and Romaine
"With a bedside manner like that, Scotty, you're in the wrong business."
- - Chapel, before leaving him and Romaine in sickbay
"Is the doctor there with you, or will I find him in engineering?"
- - Kirk to Scott, on his dereliction of duty
"Doctor McCoy can no more cure it than he can a cold."
- - Scott, convincing Romaine not to report her visions
"I'd rather die than hurt you. I'd rather die!"
- - Romaine to Scott, on foretelling his death
"Somehow, I find transporting into the darkness unnerving."
- - McCoy when the landing party beams down to a dark Memory Alpha
"Mira will not kill me."
- - Scott, before placing Romaine in the chamber
"Reduce the pressure very, very gradually, Spock."
"We may tax Mister Scott's patience, doctor."
- - McCoy and Spock, on ending Romaine's treatment
"Now we have all the time in the world."
- - Scott to Kirk, on Romaine
"Humans do claim a great deal for that particular emotion."
- - Spock to Kirk, on love as a factor in Romaine's recovery
"Mister Scott, how's Lieutenant Romaine?"
- - Kirk and Scott
"Well, this is an Enterprise first. Doctor McCoy, Mister Spock, and Engineer Scott find themselves in complete agreement. Can I stand the strain?"
- - Kirk
Script and production
- The co-writer of this episode was ventriloquist and puppeteer Shari Lewis of "Lamb Chop" fame. A fan of Star Trek, she co-wrote this episode with her husband Jeremy Tarcher. She also wanted to play Mira Romaine, but was not cast. 
- When Lewis originally pitched the idea to producer Fred Freiberger, he turned it down, saying that they were already working on a similar concept. When Lewis came back with another story idea, Freiberger told her that he'd buy the first one, because the other similar project had been scrapped. 
- Lewis wrote Scott's love affair into the episode because she thought "Captain Kirk is the one who always gets the girl". 
- In a story outline dated 12 September 1968, Romaine was Scott's new engineering assistant and shared his fascination for machinery. Final draft script 28 October 1968, filmed early November.
- The overhead zoom shot of the bridge in the teaser was not shot for this episode. It apparently was filmed for (but not used in) "The Galileo Seven". Bill Blackburn, rather than Walter Koenig, is at the navigator station in the shot. It is noticeable that he is wearing lieutenant stripes in the shot. The crew is also noticeably wearing the velour uniforms seen in season 1 and 2, not the nylon variety that replaced them in season 3.
- There is extensive use of Alexander Courage's music from "Where No Man Has Gone Before" in this episode. Most notable is the piece used for the approach of the Zetarians which was scored for the "Where No Man…" scene when the Enterprise encounters the galactic barrier.
- This is the only episode of The Original Series in which the four principal personnel of the Enterprise (Kirk, Spock, McCoy, and Scott) beam down from the ship without any supporting crewmembers.
Sets and props
- This is the last time the emergency manual monitor and engineering sets were used. Engineering was seen briefly in "The Savage Curtain", but as stock footage.
- This is the only time more of Dr. McCoy's medical lab, including an antigrav tube, is seen.
- The Memory Alpha monitor room was the reused control room set from "Whom Gods Destroy".
- The glass-covered portal of the medical decompression chamber appears to be a door left over from a suspended-animation pod in "Space Seed".
- During the tag in sickbay as Kirk, Spock, and McCoy discuss Lt. Romaine, a discarded newspaper can be seen through the doorway to next room lying on the floor (to the right of Nimoy's elbow).
- This was John Winston's only appearance during Star Trek's final season. It is also the only episode in which he appears in addition to all eight regulars, including Christine Chapel.
- Additionally, this is the final episode in which a Tellarite and an Andorian appears in TOS.
- The Human-looking female Memory Alpha technician was originally scripted as being a member of a species known as the "Reidonians". 
- All the scenes of Scott while Lt. Romaine is being treated in the chamber in the medical lab show him with a Sciences style chest insignia (with a stylized "globe," as Spock and Dr. McCoy would wear) as opposed to the usual "spiral" on his red duty uniform.
- Ronald D. Moore once cited this episode as his least favorite installment of the original Star Trek series, saying that it "doesn't even have the campy fun of 'Spock's Brain' to get you through it." (Star Trek: The Magazine Volume 1, Issue 1, p. 112)
"The Lights of Zetar" was the seventy-second episode of the remastered version of The Original Series to air. It premiered in syndication on the weekend of 7 June 2008 and aside from the standard CGI replacement footage of the Enterprise, this episode most notably featured new effects shots of the Zetarians and Memory Alpha, which included the appearance of the library complex, where none had appeared before.
According to Michael Okuda: "Based on the size and spacing of the windows, I'd estimate that each of the domes must be similar to the Superdome." Also, "if you look very closely at the far left dome, you might notice a small blue patch on the top of the dome. That's the Memory Alpha emblem." 
- The next remastered episode to air was "The Way to Eden".
- The third book in Wallace Moore's "Balzan of the Cat People" pulp SF series, 1975's "The Lights of Zetar," was apparently an homage to this episode.
- Star Trek Novel #42, Memory Prime by Gar and Judith Reeves-Stevens, continues the story of Romaine on Memory Prime, the successor to Memory Alpha. Other than her romance with Scott and a very brief mention of the Zetarians, no other story elements are carried over from the episode.
- The short story "Ancient History" in the Strange New Worlds VI anthology portrayed Scott and Captain Morgan Bateson, both catapulted into the future by their respective mishaps, meeting and hashing out, physically and verbally, old rivalries, one of which was based on the fact that Mira Romaine married Bateson after her relationship with Scott had ended.
- Story outline by Shari Lewis and Jeremy Tarcher, titled "Sentry 7", 22 August 1968
- Revised story outline, titled "The Lights of Zetar", 6 September 1968
- Second revised story outline, 12 September 1968
- First draft teleplay, 8 October 1968
- Second draft teleplay, mid-October 1968
- Final draft teleplay by Arthur Singer, 28 October 1968
- Additional page revisions by Fred Freiberger, 30 October 1968, 31 October 1968, 1 November 1968, 4 November 1968, 8 November 1968
- Filmed, 1 November 1968 – 11 November 1968
- Day 1 – 1 November 1968, Friday – Desilu Stage 9: Int. Bridge
- Day 2 – 4 November 1968, Monday – Desilu Stage 9: Int. Bridge, Corridors
- Day 3 – 5 November 1968, Tuesday – Desilu Stage 9: Int. Briefing room
- Day 4 – 6 November 1968, Wednesday – Desilu Stage 9: Int. Briefing room, Sickbay, Transporter room
- Day 5 – 7 November 1968, Thursday – Desilu Stage 9: Int. Medical lab (with the Decompression chamber)
- Day 6 – 8 November 1968, Friday – Desilu Stage 9: Int. Medical lab (with the Decompression chamber), Briefing room, Emergency manual control
- Day 7 – 11 November 1968, Monday – Desilu Stage 9: Int. Emergency manual control; Desilu Stage 10: Int. Memory Alpha control room
- Original airdate, 31 January 1969
- Rerun airdate, 26 August 1969
- First UK airdate 17 November 1971
During the syndication run of Star Trek, no syndication cuts were made to this episode.
Video and DVD releases
- Original US Betamax release: 1988
- UK VHS release (two-episode tapes, CIC Video): Volume 38, catalog number VHR 2434, 4 February 1991
- US VHS release: 15 April 1994
- UK re-release (three-episode tapes, CIC Video): Volume 3.6, 5 January 1998
- Original US DVD release (single-disc): Volume 37, 27 November 2001
- As part of the TOS Season 3 DVD collection
- As part of the TOS-R Season 3 DVD collection
Links and references
- Jan Shutan as Lt. Mira Romaine
- James Doohan as Scott
- George Takei as Sulu
- Walter Koenig as Chekov
- Nichelle Nichols as Uhura
- Majel Barrett as Nurse Chapel
- John Winston as Lt. Kyle
- Libby Erwin as Technician
- Majel Barrett as Computer Voice
- William Blackburn as Hadley
- Frank da Vinci as Brent
- Roger Holloway as Roger Lemli
- Jeannie Malone as Yeoman
- Barbara Babcock as voice of the Zetarians
- Unknown actors as
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- "The Lights of Zetar" at StarTrek.com, the official Star Trek website
- "The Lights of Zetar" at Memory Beta, the wiki for licensed Star Trek works
- "The Lights of Zetar" at Wikipedia
- "The Lights of Zetar" at MissionLogPodcast.com, a Roddenberry Star Trek podcast
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