(written from a Production point of view)
The Enterprise discovers a generational asteroid ship on a collision course with an inhabited planet.
At red alert, the USS Enterprise detects an approaching spread of primitive, chemical fueled, sublight nuclear missiles, which are quickly destroyed by its phasers. The crew traces the origin of the missile's path. Captain Kirk orders Ensign Chekov to plot a course, for the Enterprise to proceed, at warp factor 3 to the launchers. Meanwhile, during Dr. McCoy's routine health check, a rare terminal illness, xenopolycythemia, is discovered. They do not know its cure. It will kill him within a year. McCoy insists that he can remain in his post on the Enterprise, but Kirk immediately informs Starfleet and requests a replacement.
Enterprise arrives at the location of the missile launch, where they see an asteroid, two hundred miles in diameter. Oddly, it is not in any orbit but follows an independent course through the local star system. Its course, 241-mark-17, leads it in 396 days, to the planet Daran V, where it will collide and kill its population of 3.724 billion. Before destroying the asteroid, to prevent the collision, they scan it and learn it is an atomic-powered spaceship. They do not detect living beings. Spock guesses that the passengers are dead. The Enterprise charts a course parallel to it.
Kirk and Spock enter the transporter room, and prepare to beam onto the asteroid/spaceship. McCoy insists on joining them so the arrive inside the asteroid. They find a surface that appears geologically active, with a reddish sky, and are puzzled that the builders apparently wanted the inside of the ship to look just like the surface of a planet. The surface has large orange cylinders, from which primitive, sword-bearing men emerge. Their leader is a beautiful woman. After a brief melee, Kirk, McCoy and Spock get captured. McCoy shares a meaningful look with the leader, before he is knocked unconscious.
The beautiful woman introduces herself as Natira, the high priestess and leader of her people. Natira "welcomes" the officers to their world Yonada. The three are taken below the surface, where they encounter a large population of young and apparently healthy people. Natira leads the three into an Oracle Room, where she consults an unseen authoritative entity manifested by a decorative altar and a booming voice. Kirk and McCoy estimate that after ten thousand years in this multi-generational ship, the people no longer realize they are inside a spaceship. The Oracle "punishes" Kirk, Spock, and McCoy by shocking them with an energy beam, rendering them unconscious.
The three regain consciousness, although McCoy remains out longer due to his illness, in some sort of guest area. Kirk then informs Spock about McCoy's condition. An old man enters the room and gives them an herb derivative to counteract the effects of the Oracle's attack, noting that many people on the ship have been punished in this way. When they tell him they are not from Yonada, he recalls how he once climbed the mountains, "even though it is forbidden," and found that the world of Yonada is not a planet at all. "For the world is hollow and I have touched the sky…", he says before collapsing to the ground. He dies immediately, apparently from a subcutaneous control device in his temple. Natira comes in, has the old man's body gently taken away, and seems to take a special interest in McCoy. Kirk recommends that McCoy use this to their advantage so that they may learn more about the civilization. The captain is faced with a triple dilemma: either risk violating the Prime Directive by informing the people of Yonada of their situation, destroy the asteroid with them in it, or allow it to destroy Daran V. Natira admits she is in love with McCoy and wants him to stay on Yonada as her mate. She speaks of a final destination that is rich and green and notes that the Oracle has promised they shall reach it "soon." When McCoy tells her he has only a year to live, she tells him even a day, a month, or a year with him will make her happy.
Spock and Kirk make their way to the Oracle Room, and Spock recognizes the writing as that of the Fabrini, a civilization wiped out ten thousand years prior, when their star went nova. He also sees a symbolic map of the Fabrina solar system. Prior to dying out, the Fabrini had lived underground to protect themselves. They had also built this spaceship Yonada and programmed the Oracle of the People, which is actually a powerful computer, to take their surviving civilization to another habitable planet. The people of Yonada are their descendants. Spock manages to open the door, and the two conceal themselves in the temple behind a monolith as Natira enters. She asks the Oracle for permission to marry McCoy. The Oracle grants it, so long as McCoy agrees to join the Fabrini and submit to the instrument of obedience to become one of their people. As she's leaving, however, the Oracle discovers Kirk and Spock and zaps them. They are arrested and sentenced to death.
McCoy agrees to stay on Yonada but begs that Kirk and Spock be released. McCoy tells her he could never be happy on Yonada knowing that his two friends had died for his happiness. Natira agrees. As Kirk and Spock prepare to return, McCoy insists on staying. Kirk and McCoy briefly argue about his decision but Kirk agrees to leave him behind. He and Spock return to the Enterprise. In a ritual with the Oracle, McCoy has the instrument of obedience implanted in his head and he and Natira are married. At the Oracle's command, she reveals to him an ancient book that is to be opened and read when the ship reaches the "New World of the Promise." Meanwhile, Kirk consults with Admiral Westervliet on a monitor in his quarters, who relieves him of all responsibility for the Yonada, saying that Starfleet Command will handle the situation. McCoy calls the ship with his communicator and tries to explain that by consulting the book Spock can change the Yonada's course. His instrument of obedience immediately sends him a shock of pain. He passes out as Natira enters.
Kirk and Spock beam back to the Yonada and Spock removes McCoy's instrument of obedience, shocking Natira. She tries to call for the guards, but Kirk subdues her and persuades her to give them a chance. He explains the history of the Fabrini and Yonada. She is very skeptical of the story and the Oracle begins to torment her through her instrument. She flees, but does not turn Kirk and Spock over to the guards. Kirk and Spock have found that a faulty part of the Oracle computer has caused a change in course. Natira consults the Oracle, which knocks her out. When Kirk, Spock, and McCoy arrive, she says she believes them and McCoy removes her instrument. Kirk and Spock move to take the book out of the temple, but the Oracle fights them, kicking up a storm and increasing the temperature in the room to 120 degrees, planning to burn them to death or until they die of heat stroke. McCoy shows them how to open the pylon containing the book and Spock uses the book to disable the heating element, as well as the Oracle, and reprogram the spaceship's course.
McCoy and Natira share a tearful farewell: She must stay to lead her people to the promised land and McCoy is determined to keep traveling the universe in search of a cure for his disease as well as for others afflicted. After correcting the Yonada's course, Spock shows Kirk the cylinders containing the vast database of the Fabrini, which contains medical knowledge, including the cure for xenopolycythemia. McCoy undergoes the very painful treatment for his illness, with Nurse Chapel at his side in the Enterprise's sickbay. When McCoy emerges cured, Kirk promises him the Enterprise will soon return to the area in 390 days when the Yonada eventually reaches its correct destination. McCoy is pleased by Kirk's promise and the Enterprise leaves Yonada.
- "Captain's log, stardate 5476.3. I have just had the sad duty of informing Starfleet about Dr. McCoy's condition and have requested an immediate replacement."
- "Captain's log, stardate 5476.4. We are on a parallel course with Yonada. It is still on a collision course with Daran V. Our failure to correct its course, and the critical nature of Dr. McCoy's illness, made the extraordinary event of contact with Starfleet Command imperative."
"A lot can happen in a year. Please, give yourself every minute."
- - Chapel to McCoy, on his illness
"Welcome to the world of Yonada."
"I can't say I think much of your welcome."
- - Natira and Kirk, after the ambush on the landing party
"We've come in friendship."
"Then learn what it means to be our enemy before you learn what it means to be our friend."
- - Kirk and the Oracle, as it punishes the landing party
"But things are not as they teach us. For the world is hollow, and I have touched the sky."
- - Fabrini man's last words
"Forgive him for he was an old man, and old men are sometimes foolish."
- - Natira, as she prays by the Fabrini man's body
"But we're strangers to each other."
"But is not that the nature of men and women? That the pleasure is in the learning of each other?"
- - McCoy and Natira, as she asks him to be her mate
"Until I saw you, there was nothing in my heart. It sustained my life, but nothing more. Now it sings. I could be happy to have that feeling for a day, a week, a month, a year."
- - Natira, before kissing McCoy
"Kirk and Spock have committed sacrilege. You know what must be done."
- - Oracle, to Natira when it discovers Kirk and Spock have broken into its room
"Is truth not truth for all?"
- - Natira, challenging the Oracle
"Captain, informing these people they are on a ship may be a violation of the prime directive of Starfleet Command."
"Well the people of Yonada may be changed by the knowledge, but it's better than exterminating them."
- -Spock and Kirk, on whether or not to inform the Fabrini of their situation
- The idea of a multi-generational spaceship or "interstellar ark" is an old one that was first proposed in an unpublished paper by Robert Goddard in 1918. Goddard's fellow rocket pioneers Konstantin Tsiolkovsky and J.D. Bernal also considered the idea in the 1920s. Olaf Stapledon and Don Wilcox wrote stories about the idea in the 1940s, and Robert Heinlein originated the notion that inhabitants might forget they were on a ship in his book Orphans of the Sky, a concept later reused by Harlan Ellison in his story Phoenix Without Ashes, which was adapted into the 1973 television series The Starlost starring Keir Dullea and guest-starred Walter Koenig in a recurring role.
- The prop used as Book of the People is the same one used as Chicago Mobs of the Twenties in "A Piece of the Action".
- The metal helical staircase is recycled from "The Empath".
- The scenes of Yonada are reused footage of the asteroid from "The Paradise Syndrome", and the helical staircase in the control room at the end of this episode seems to be the same one used inside the Obelisk in that same episode.
- This is the only series episode to feature three actors who appeared in the original pilot "The Cage": Leonard Nimoy (Spock), Majel Barrett (Christine Chapel) and Jon Lormer (old man) (not including "The Menagerie, Part I" and "The Menagerie, Part II", which features much footage from "The Cage"). Barrett and Lormer played Number One and Theodore Haskins, respectively, in the pilot.
- Whether by chance or design, the music that accompanies the appearance of the old man played by Jon Lormer is the same music by Alexander Courage that played during some of his lines as Dr. Theodore Haskins in "The Cage".
- To give more depth to the planet set, the entrances to the underground civilization were built in two sizes: those in the distance were constructed much smaller, thus creating an illusion of distance.
- The bridge scene that runs under Kirk's voiceover at the start of Act One – where Kirk enters the bridge from the turboshaft – is the same footage from the very beginning of the episode.
- The field reader tube, normally used to take a medical patient's vital signs, is used in this episode by Spock to extract McCoy's instrument of obedience and by McCoy to extract Natira's. These mark the only apparent close-up uses of this prop in the series.
- In the trailer, the scene where the Oracle turns on the heat plays without the red overlay or the heat-wave distortion effect.
- According to a call sheet, Dick Geary appeared as a security guard in this episode, but it seems his appearance ended up as a deleted scene. 
- This episode has the longest title of any episode in any Star Trek series.
- In an early story outline (2 May 1968), it was Scott who was ill.
- According to the novel The Sorrows of Empire, McCoy's mirror universe counterpart died of xenopolycythemia in 2269, as the ISS Enterprise either never encountered or destroyed the Fabrini ship. He was succeeded as chief medical officer by the mirror universe counterpart of Dr. M'Benga, who continued to serve in that position until at least 2287.
- According to the listing of Star Trek: New Voyages episodes, a sequel to this episode entitled "Torment of Destiny" is unfinished.
- The remastered version of this episode premiered in syndication the weekend of 29 January 2007 and featured shots of a digital version of Yonada, more closely resembling real asteroids. The battle between the Enterprise and the missiles was also revamped digitally.
- The next remastered episode to air was "Journey to Babel".
- Story outline by Rik Vollaerts, 2 May 1968
- Revised story outline, 4 May 1968
- Second revised story outline, 21 May 1968
- First draft teleplay, early-June 1968
- Second draft teleplay, 17 June 1968
- Revised second draft teleplay, 1 July 1968
- Second revised second draft teleplay, 31 July 1968
- Final draft script – 2 August 1968
- Final draft teleplay by Arthur Singer, 7 August 1968, 8 August 1968, 9 August 1968
- Additional page revisions by Fred Freiberger, 12 August 1968, 13 August 1968, 14 August 1968
- Filmed, 13 August 1968 – 22 August 1968
- Day 1 – 13 August 1968, Tuesday – Desilu Stage 9: Int. McCoy's office, Bridge, Transporter room
- Day 2 – 14 August 1968, Wednesday – Desilu Stage 9: Int. Kirk's quarters, Sickbay; Desilu Stage 10: "Ext". Yonada surface
- Day 3 – 15 August 1968, Thursday – Desilu Culver Stage 8: Int. Fabrini corridors, Oracle room, Fabrini corridors, Natira's quarters
- Day 4 – 16 August 1968, Friday – Desilu Culver Stage 8: Int. Natira's quarters, Oracle room
- Day 5 – 19 August 1968, Monday – Desilu Culver Stage 8: Int. Oracle room, Guest quarters
- Day 6 – 20 August 1968, Tuesday – Desilu Culver Stage 8: Int.Guest quarters
- Day 7 – 21 August 1968, Wednesday – Desilu Culver Stage 8: Int.Natira's quarters, Oracle room
- Day 8 – 22 August 1968, Thursday (Half Day) – Desilu Stage 10: "Ext". Yonada surface
- Original airdate, 8 November 1968
- First UK airdate 27 October 1971
- Remastered airdate, 29 January 2007
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 34, catalog number VHR 2430, 7 January 1991
- US VHS release: 15 April 1994
- UK re-release (three-episode tapes, CIC Video): Volume 3.4, 20 October 1997
- Original US DVD release (single-disc): Volume 33, 18 September 2001
- As part of the TOS Season 3 DVD collection
- As part of the TOS-R Season 3 DVD collection
Links and references
- Katherine Woodville as Natira
- James Doohan as Scott
- George Takei as Sulu
- Walter Koenig as Chekov
- Nichelle Nichols as Uhura
- Majel Barrett as Nurse Chapel
- Byron Morrow as Admiral Westervliet
- Jon Lormer as Old Man
- Frank da Vinci as Vinci
- Dick Dial as Fabrini guard
- James Doohan as the Oracle (voice)
- Richard Geary as Security Guard (scenes deleted)
- Jeannie Malone as Fabrini servant 1
- Robert Strong as Fabrini Oracle guard 1
- Unknown performers as
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- "For the World is Hollow and I Have Touched the Sky" at StarTrek.com, the official Star Trek website
- "For the World is Hollow and I Have Touched the Sky" at Memory Beta, the wiki for licensed Star Trek works
- "For the World is Hollow and I Have Touched the Sky" at Wikipedia
- "For the World is Hollow and I Have Touched the Sky" at MissionLogPodcast.com, a Roddenberry Star Trek podcast
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