(written from a Production point of view)
The Enterprise becomes involved in a local power struggle on planet Capella IV, where the Klingons want mining rights.
The USS Enterprise approaches Capella IV, the home of the Capellans and a rich source of the rare mineral topaline. Topaline is vital to the life support systems of certain planetoid colonies. Captain Kirk's assignment from Starfleet is to obtain mining rights. Doctor McCoy, who had previously visited Capella, briefs the senior officers in the briefing room; among other things, he reveals that Capellans have a complex structure of taboos, and that they can be angered easily.
Kirk leaves Scotty in command of the Enterprise while he, Spock, McCoy and security officer Lieutenant Grant beam down and are immediately accosted by a party of Capellans led by Maab. Also in the party is Kras, a Klingon. Grant reacts too quickly, drawing his phaser, which prompts immediate retaliation: one of the warriors with Maab throws his kleegat, which hits Grant, killing him instantly.
- "Captain's log, stardate 3497.2. Planet Capella lV. The rare mineral, topaline, vital to the life support systems of planetoid colonies, has been discovered in abundance here. Our mission: obtain a mining agreement, but we've discovered a Klingon agent has preceded us to the planet. A discovery which has cost the life of one of my crewmen."
Maab demands the landing party surrender their weapons and instruments as a show of good faith. Kirk, Spock, and McCoy throw their phasers and communicators on the ground.
The landing party must wait for a period of time. Kirk expresses frustration at losing a crewman and Spock warns about getting emotional. A female Capellan enters offering a gesture of fruit, though McCoy warns not to touch it in fear of a taboo. In the meantime, on the Enterprise, Chekov thinks he detects another ship, likely the Klingons, though Scotty does not see the need to contact Kirk.
The landing party is then taken to see Akaar, who is High Teer, or leader, of the Ten Tribes of Capella. In this meeting, Kras attempts to gain the diplomatic upper hand, but McCoy's knowledge of Capellan culture trumps his efforts. Kras sneers at the Federation's offer, claiming that Capellans believe only the strong should live, just as Klingons do. Kirk retorts that the highest of Federation laws states that Capella belongs to the Capellans, and it will never be taken from them, and that Klingon space is full of worlds that learned not to trust the Klingon Empire the hard way. Maab is enthusiastic, believing that competition for the mineral can only help Capella. Akaar notes thoughtfully that in all their dealings, Earthmen have never lied to Capellans. Maab warns him that there are those who will not bargain with Earthmen, which Akaar interprets as challenge.
On the Enterprise, Uhura detects a transmission that could be a distress call, but she can't be sure.
A fight breaks out between Capellans – an armed coup. Both Maab and Akaar are involved. During the fracas, Kirk, Spock, and McCoy race to the main tent to retrieve their gear, only to discover Kras engaged in the same search. Overpowering him, Kirk learns he was sent in a small scout ship to negotiate the mineral rights for the Klingon Empire. His people need the topaline, too. Before Kirk can learn more, the fight outside is ended, and Capellans burst into the tent, demanding Kirk free Kras. Then Maab enters, declaring himself the new Teer – Akaar died in the fighting. When Kras demands he kill Kirk, Kirk suggests he fight with Kras. Now that Maab has seen fear in Kras, he is not sure about him.
On the planet, Eleen, Akaar's pregnant widow, enters the tent. Maab trips her with his sword and she burns her arm in the fire. Because she carries an heir, Maab must kill her to solidify his rule, but when he is about to do so, Kirk interferes, sparking another melee that ends with Eleen and the landing party imprisoned together. When Kirk snatched Eleen away from Maab's descending blade, he violated a taboo: no man may touch the wife of a Teer. She demands to see Kirk die before she herself is killed.
Uhura cannot reach any of the landing party, but Scotty decides to take the Enterprise out of orbit to investigate, thus stranding the landing party on Capella.
- "Captain's log, stardate 3498.9. Lieutenant Commander Scott in temporary command. We were forced to leave Capella to come to the aid of a Federation vessel under attack by a Klingon vessel. We were unable to contact our landing party before we were forced to answer the distress signal. Our inability to reach the landing party is strange. And… I am concerned."
Eleen and the landing party have been imprisoned together to await Maab's decision. Eleen is in a great deal of pain, and McCoy intends to help her. Kirk understands this is a distraction, as no one is allowed to touch her. Kirk and Spock overcome their guards and escape to the hills with Eleen. They are able to recover their communicators but not their phasers.
- "Captain's log, stardate 3499.1. Before leaving the Capellan encampment, we managed to retrieve our communicators. Our phasers were not to be found. We've fled into the hills, yet we know the Capellans will eventually find us. By scent alone, if necessary. And we've learned one thing more. The girl, Eleen, hates the unborn child she is carrying."
The landing party, with the reluctant Eleen, has taken refuge in a narrow canyon with a wide but defensible entrance and a narrow chute-like exit. McCoy demands to inspect Eleen, and slaps her to convince her of his determination, while Kirk and Spock see to their position. He determines the child could be born soon. Kirk proposes to block the entrance with a sonic disruption; two communicators linked together can produce a sympathetic vibration. This will cause a rock slide, sealing the entrance and buying time, as the Capellan search party will be forced to go around the hills to the other side. Several large rocks tumble down from the disruption, injuring many Capellans.
During the confusion, Kras manages to retrieve a phaser from one of the fallen warriors and quickly kills the Capellan with his own blade. The landing party continue on – Kirk discovers a cave in which the landing party seeks refuge.
On the Enterprise, unable to discover the source of the distress call, Scotty has Chekov pull the microtape and realizes how he has been duped: the Deirdre specifically called for the Enterprise by name – and there's no way a freighter would have known the Enterprise was ordered into this sector. Clearly, the intent was to lure the Enterprise from Capella IV. To be sure, Scotty has Sulu complete the search pattern.
In the cave, Kirk uses one of McCoy's magnasite-nitron tablets to start a fire, lighting the inside of the cave. Kirk and Spock leave McCoy there to supervise the birth, while they search for weapons. Eleen expresses frustration that the child will belong to the husband, and she does not want it to be born. McCoy attempts to convince her she wants the child and that it belongs to her. By the time Kirk and Spock have weapons fabricated, Eleen has given birth.
The Enterprise has finished its search pattern and heads back to Capella IV. Lieutenant Uhura receives another distress call, this time from the USS Carolina. Scotty ignores it, even though the Carolina is registered in the sector.
When Kirk and Spock leave to reconnoiter, Eleen hits McCoy with a rock and escapes without the child. Kirk and Spock have fabricated bows and find out what happened to McCoy. He stays with the child as they prepare to meet the Capellans.
En route to Capella IV, the Enterprise Then, a Klingon warship intercepts them – sitting in space, establishing a line and daring the Enterprise to cross it.
The Capellans have found their way to the chasm's other entrance, and the landing party have placed themselves in the rocks overlooking the cut. Before they can attack, Eleen appears. She lies to Maab, telling him all the Earthmen, and her infant son, are dead. Maab accepts her at her word, believing her to follow the Capellan code of honor, but Kras is immediately suspicious. He questions Eleen's word, angering both Maab and Eleen. When Maab refuses to verify her claim, Kras draws a stolen Starfleet phaser and offers to demonstrate to them what killing really means. During the ensuing battle, the Capellans are introduced to the bow and arrow, a weapon they never developed. Kras manages a standoff; to break it, Eleen proposes to flee as a sacrifice and a distraction. Maab elects to return her life to her, which forfeits his own. He advances upon the Klingon and sacrifices himself to draw Kras' fire: his lieutenant Keel is ready and kills the Klingon in the chest with a kleegat.
As the confrontation is about to conclude badly, Scotty and a rescue party appear, pointing their phasers at them and demand the Capellans' surrender. McCoy appears from the hills with the new Teer, Leonard James Akaar. Eleen signs the mining agreement as regent for the new Teer, and the Starfleet team beams back to the Enterprise. On the bridge of the Enterprise, Kirk and McCoy remark with pride on how the new Teer of Capella IV is named after them both. Spock remarks that they will both be insufferably pleased with themselves for at least a month. The Enterprise then departs Capella IV.
- "Captain's Log, stardate 3497.2. Planet Capella Four. The rare mineral topaline, vital to the life-support systems of planetoid colonies, has been discovered in abundance here. Our mission, obtain a mining agreement. But we've discovered a Klingon agent has preceded us to the planet. A discovery which has cost the life of one of my crewmen.
- "Captain's Log, stardate 3498.9. Lieutenant Commander Scott in temporary command. We were forced to leave Capella to come to the aid of a Federation vessel under attack by a Klingon vessel. We were unable to contact our landing party before we were forced to answer the distress signal. Our inability to reach the landing party is strange, and… I am concerned."
- "Captain's Log, stardate 3499.1. Before leaving the Capellan encampment, we managed to retrieve our communicators. Our phasers were not to be found. We have fled into the hills, yet we know the Capellans will eventually find us, by scent alone if necessary. And we have learned one thing more: The girl, Eleen, hates the unborn child she is carrying."
"What the Klingon has said is unimportant, and we do not hear his words."
- - McCoy, calling Kras a liar to Akaar
"Yes, you're quite right, Mr. Spock. Inefficient – and illogical."
- - Kirk, when Spock tells him of the inefficiency of emotion
"Perhaps to be a Teer is to see in new ways. I begin to like you, Earthman… and I saw fear in the Klingon's eye."
- - Maab, upon becoming the new ruler of the Ten Tribes
"Look, I'm a doctor, not an escalator!"
- - McCoy to Spock, as Eleen struggles to climb a steep incline
"How did you arrange to touch her, Bones? Give her a happy pill?"
"No, a right cross."
- - Kirk and McCoy, as McCoy examines Eleen
"Say to yourself, the child is mine. The child is mine. It is mine!"
"Yes, it's yours.'"
- - McCoy and Eleen, as she misunderstands what he said
"Fortunately, this bark has suitable tensile cohesion."
"You mean it makes a good bowstring."
"I believe I said that."
- - Spock and Kirk, as they test their bows
"McCoy. Bring our child."
"I'll explain later."
- - Eleen, Kirk, and McCoy, after the baby is born
"There's an old, old saying on Earth, Mister Sulu. Fool me once, shame on you. Fool me twice, shame on me."
"I know this saying. It was inwented in Russia."
- - Scott and Chekov, after Scott decides to ignore the second distress call
"The cavalry doesn't come over the hill in the nick of time anymore."
- - Kirk, as Spock hails the Enterprise
"Oochy-woochy coochy-coo, captain?"
"An obscure Earth dialect, Mister Spock. Oochy-coochy coochy-coo. If you're curious, consult linguistics."
- - Spock and Kirk, when McCoy coos to the baby Spock repeats it puzzled and Kirk repeats it incorrectly
"The child was named Leonard James Akaar?"
"Has a kind of a ring to it, don't you think, James?"
"Yes. I think it's a name destined to go down in galactic history, Leonard. What do you think, Spock?"
"I think you're both going to be insufferably pleased with yourselves for at least a month… sir."
- - Spock, McCoy, and Kirk, as Kirk and McCoy brag about their connection to the child
- Exterior planet scenes were filmed at the familiar Vasquez Rocks Natural Area Park, located North of Los Angeles. (Star Trek Encyclopedia (2nd ed., p. 63))
- The episode was filmed in late May amid temperatures at Vasquez Rocks of up to 110 degrees, making it highly uncomfortable for actors, especially those in Capellan costumes. However, Tige Andrews enjoyed his Klingon costume very much, this being his first chance to wear a non-ordinary costume for a film role. His exotic demeanor helped him get into the character of Kras. 
- In Dorothy Fontana's original script, Eleen sacrificed her child for her own life. Gene Roddenberry objected to this, and changed the ending to what appears in the finished episode. Fontana also envisioned Eleen as a strong woman, who rebels against a society which considers women only as mothers and homemakers. 
- The set panel to the left of the science station was removed for this episode. Chekov can be seen with his hand draped over the left edge of the station; an edge that shouldn't exist. In the next episode, "Who Mourns for Adonais?", wider shots show that the workstation counter top continues unbroken when the set piece is in place. For the "Friday's Child" remastered edition, a close up of the science station replaces the old, incomplete, version.
- In the briefing room footage of Dr. McCoy's previous visit to Capella IV, he is wearing his present-day Starfleet uniform, rather than a uniform specific to Starfleet circa 2265 (TOS: "Where No Man Has Gone Before"). This assumes McCoy was stationed on the planet prior to his assignment as the Enterprise's chief medical officer. However, because McCoy does not appear in the TOS Season 1 episodes TOS: "What Are Little Girls Made Of?" and TOS: "Errand of Mercy", and because the duration of his assignment was "only a few months," it's possible he was temporarily transferred to Capella IV during one (or both) of those time periods, meaning his uniform is correct.
- Leonard James Akaar has appeared as an influential Starfleet admiral in several of the Star Trek: Deep Space Nine novels that take place after the end of the events depicted on screen, suggesting Kirk's half-joking prediction of the name going down in history did in fact come true, to some extent.
- This is the first episode which Chekov makes the dubious claim of something being invented in Russia. In this case he claims that the old Earth saying: "Fool me once, shame on you. Fool me twice, shame on me," was invented in Russia. He does so with a smirk, suggesting he may only be teasing.
- The footage seen on the briefing room screen in the teaser is recycled from scenes of the warriors hunting down Kirk and company later on in the episode.
- Actors playing Capellan warriors were given elevated shoes to make them appear as "giants" compared to Humans and Klingons. Maab's high-top headwear served the same purpose. 
- A sequence in the blooper reel shows William Shatner entering the tent too quickly when Tige Andrews is looking for his weapon and exclaiming, "Oh, shit!"
- Lots of dialogue looping was used in this episode because of the outdoor setting. Some of the dubbing was crammed together, nearly on top of other lines.
- By preventing Maab from killing Eleen, thereby allowing her unborn son to become Teer of the tribes, Kirk and company would appear to be in flagrant violation of the Prime Directive. This is discussed in the TOS comic The Trial of James T. Kirk, where Akaar is called to testify. He states that he believes in the wisdom of the man who saved his life, namely Kirk. He then kneels before Kirk to demonstrate the depth of his gratitude.
- In the TOS comic The Peacekeeper Part Two: The Conclusion, the events of this episode are mentioned by Dr. McCoy in order to motivate Captain Kirk to make an exception in the Prime Directive, suggesting that it was violated in this episode.
- For his first four appearances in the series, including this episode, Walter Koenig wore a Monkees-style wig, which he absolutely detested. In one interview, he made joking and uncomplimentary references to that wig. By "The Apple", he seems to have discarded it.
- This was Robert Bralver's first appearance of many in the series, often as a stunt performer or uncredited extra.
- This episode marks the debut of Sulu's personal scanner at his helm position. In its first appearance, the device is seen slowly unfolding as it emerges from inside the helm console. In his written adaptations of the episodes, James Blish refers to the device as a "gooseneck viewer."
- Stephen Whitfield's The Making of Star Trek and David Gerrold's The World of Star Trek incorrectly lists this episode's first airdate as 22 March 1967.
- Stephen Whitfield's The Making of Star Trek also features some excellent behind-the-scenes photos from this episode, filmed in late May 1967.
- The name of this episode derives from the 1887 Harper's Weekly version of the old children's rhyme, Monday's Child, which includes the line "Friday's child is full of woe."
- "Capellans" was also the name given to the aliens in Jerry Sohl's 1953 novel The Transcendent Man, though the connection seems unintentional: the aliens in that book were closer in style to the Organians. Capella itself is the brightest star in the constellation of Auriga, the charioteer.
- There is an interesting sequence in the latter part of the episode. As Maab and his cohorts close in on Kirk's hideout, Tige Andrews takes a face-forward flop onto the ground. In the next close-up, he is seen in the background getting up, and after a cutaway, comes to the foreground and dusts off his pants. This would seem to indicate that for the close-up coverage, there was a second camera filming simultaneously to the wide shot, and that the camera was hidden behind the large rock seen near Michael Dante.
- This is the first episode where Spock is knocked out in a fight (the second and final being "Mirror, Mirror", though in that case it is the mirror who is incapacitated) where a Capellan hits the Vulcan with a sword while he and Kirk prevent Eleen's death.
- This is the first episode where all seven "classic" crew members (Kirk, Spock, McCoy, Scotty, Uhura, Sulu, and Chekov) appear in the same scene, in the teaser, discussing the background for the Capellans, although Sulu is seen only on a view screen reporting from the bridge. The other six are all in the same briefing room together. The six also appear in the same scene together at the very end on the bridge, and George Takei is still absent, although the right arm of a helmsman that should be Sulu is seen at the right edge of the screen.
- Story outline by D.C. Fontana: 11 January 1967
- First draft teleplay: 17 March 1967
- Second draft teleplay: 19 April 1967
- Revised second draft: 20 April 1967
- Final draft teleplay by Gene L. Coon: early-May 1967
- Revised final draft by Gene Roddenberry: 11 May 1967
- Additional page revisions by Coon: 18 May 1967
- Filmed: 19 May 1967 – 29 May 1967
- Day 1 – 19 May 1967, Friday (Half Day) – Desilu Stage 9: Int. Briefing room, Bridge
- Day 2 – 22 May 1967, Monday – Desilu Stage 9: Ext. Outside cave, Int. Bridge
- Day 3 – 23 May 1967, Tuesday – Desilu Stage 9: Int. Bridge
- Day 4 – 24 May 1967, Wednesday – Vasquez Rocks Natural Area Park: Ext. Capella IV surface (canyon)
- Day 5 – 25 May 1967, Thursday – Vasquez Rocks Natural Area Park: Ext. Capella IV surface (canyon)
- Day 6 – 26 May 1967, Friday – Desilu Stage 10: Ext. Capellan camp, Ext. Tent, Int. Kirk's tent
- Day 7 – 29 May 1967, Monday – Desilu Stage 10: Int. Akaar's tent
- Score recording: 7 July 1967
- Premiere airdate: 1 December 1967
- First UK airdate: 14 October 1970
- Remastered airdate: 6 January 2007
- The remastered version of this episode premiered in syndication the weekend of 6 January 2007. Among new shots of the Enterprise herself, several new, more realistic views of Capella IV from space were inserted into the episode. Other changes include cleaned up mattes of the viewscreen during the briefing room scene, a more realistic sensor readout on the bridge, a corrected insert shot while Chekov is working the controls at the science station, updated phaser effects, and the establishment of the Klingon ship on screen as a D7-class.
Video and DVD releases
- Original US Betamax release: 1986
- UK VHS release (two-episode tapes, CIC Video): Volume 17, catalog number VHR 2329, release date unknown
- US VHS release: 15 April 1994
- UK re-release (three-episode tapes, CIC Video): Volume 2.1, 3 February 1997
- Original US DVD release (single-disc): Volume 16, 19 September 2000
- As part of the TOS Season 2 DVD collection
- As part of the TOS-R Season 2 DVD collection: 5 August 2008 (Region 1), 27 April 2009 (Region 2)
Links and references
- James Doohan as Scott
- George Takei as Sulu
- Nichelle Nichols as Uhura
- Cal Bolder as Keel
- Ben Gage as Akaar
- Walter Koenig as Chekov
- Kirk Raymone as Duur
- Robert Bralver as Grant
- William Blackburn as Hadley
- Walker Edmiston as Officer (voice)
- Eddie Paskey as Leslie
- Unknown actors as
- Chuck Clow as the stunt double for William Shatner
- Dick Dial as Warrior's stunt double
- Jay Jones as the stunt double for Tige Andrews
"all right"; amusement; analysis; area; arm; "at best"; "at any rate"; back; bargain; bark; battle stations; "bear in mind"; belly; belt; "Bones"; booster; bow and arrow; bowstring; Capella IV; Capella IV sector; Capella IV village; Capellans; Capellan language; Capellan law; Carolina, USS; cavalry; cave; chance; check-in signal; "chewed you out"; childbirth; children; choice; combat; commander; communication channel; communicator; conclusion; contact; convoy ship; course; custom; death; debris; device; dialect; Dierdre, SS; disappointment; distance; distress signal (aka distress call); doctor; document; "drawing a line"; Earth; Earth Federation; emergency; emotion; encampment; enemy; entrance; escalator; estimating; exit; fear; Federation law; feet; flight path; "Fool me once, shame on you. Fool me twice, shame on me."; freighter; frequency; friend; friendship; galactic history; gesture; goods; guest; gunpowder; "ham-handed"; hand; happy pill; hate; head; heart; High Chief; High Teer (Teer); hill; hospital; hour; Human (aka Earthman or Earth people); humanoid; idea; "I'm a doctor, not a..."; instinct; intention; interception course; "in the nick of time"; "just a minute"; "kind of a ring"; kleegat; Klingon; Klingon agent (agent); Klingon Empire; Klingon scout ship/warship; knife; landing party; laughter; liar; life support system; line of flight; linguistics; liquid; location; logic; love; magnasite-nitron tablet; maximum speed; "make no mistake"; medical aid; medical book; medical kit; medical oath; microtape; mineral; mining; mining right; mining treaty (aka mining agreement); minute; mission; mistake; month; name; namesake; negotiation; "not move a muscle"; "on our toes"; "Oochy-woochy coochy-coo"; pain; patient; phaser; phaser bank; place; planetoid colony; "playing cat and mouse"; policy; powder; psychiatry; reconnaissance party; regent; relative term; report; revenge; right cross; rock; Russia; saying; scent; Scots language; scout ship; search pattern; sensor; sensor range; sensor report; shale; shame; shelter; sight; ship's captain; sky; sonic disruption; sound beam; standard orbit; "stand by"; starship; state of war; stomach; story; sublight; surgery; sword; sympathetic vibration; taboo; tensile cohesion; tent; Ten Tribes; "thank you"; thing; throat; topaline; tradition; trail; trap; tribe; truth; vegetation; viewscreen; village; virtue; wall; warrior; water; weapons; "wee"; widow; word; yard; youth
- "Friday's Child" at StarTrek.com, the official Star Trek website
- "Friday's Child" at Memory Beta, the wiki for licensed Star Trek works
- "Friday's Child" at Wikipedia
- "Friday's Child" at MissionLogPodcast.com, a Roddenberry Star Trek podcast
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