[[caption-width-right:320:''"As it was in the dawn of our days, as it is today, as it will be for all tomorrows, I make my choice. This one.''"]]

We start off with [=McCoy=] catching Kirk on his rounds to talk about how un-Vulcanlike Spock's been for the past couple of days. Kirk at first dismisses [=McCoy=]'s worries as being nothing... until another ill-fated attempt by Nurse Chapel to gain his eye causes Spock to throw a temper tantrum, catching everyone by surprise. Unfortunately, the green-blooded primadonna refuses to let in on what's causing his behavior, only demanding leave on his home planet.

Nothing doing, though; the ''Enterprise'' is on its way to represent the Federation at the crowning ceremony for the new ruler of Altair VI, which has been bumped up by a few days - nowhere near enough time for a detour to Vulcan. Spock, however, won't take "no" for an answer, and defies orders to head to Vulcan, anyway, forcing Kirk to order him to [=McCoy=]'s for a checkup to see just what the hell is wrong with him.

It turns out that Spock has hit that time of the decade where Vulcans need to return home and mate. If he can't, the massively elevated levels of adrenaline and other hormones will kill him within a week. Kirk, sympathetic, tries to talk to Starfleet about a quick detour to Vulcan, but his refusal to go into Vulcan reproductive habits (why no one in the Federation didn't know about them until now, what with Vulcans being one of the ''founding members'' of the organization and all, I have no idea) doesn't convince them. [[ScrewTheRulesImDoingWhatsRight Kirk, having made his own assessment of the situation, decides they can do without the Enterprise for a bit and heads to Vulcan anyway.]]

Once at Vulcan, Spock introduces the crew to T'Pring, his wife-to-be, and offers an invitation to both Kirk and [=McCoy=](?) to the wedding ceremony. Arriving at Spock's ancestral home, they learn that T'Pau, ''the'' face of Vulcan, and the only person ever to decline a seat on the Federation council, is overseeing the proceedings. Then T'Pring throws a spanner in the works by invoking a rule allowing her to refuse her husband-to-be unless he proves his worth by fighting a champion of her choice -- and she chooses Kirk. Although he is offered an opportunity to decline, since he's not a Vulcan and needn't be bound by Vulcan law, Kirk accepts, intending to either knock Spock out or find a way of taking a dive. It's only after he's accepted that anybody thinks to mention that the fight is -- of course -- to the ''death''. A protracted fight scene between the two friends ends with Spock seemingly killing Kirk after [=McCoy=] gives him something to help fight in the more hostile environment of the planet.

With the shock of killing his best friend acting like a bucket of cold water on the horny Vulcan, Spock orders Kirk's body and [=McCoy=] back to the ship while he confronts T'Pring on her choice; turns out, T'Pring hated the idea of marrying for money and fame, and fell in love with a more obscurely-known Vulcan male named Stonn, and arranged everything so that, [[XanatosGambit regardless of the outcome, she'd be able to stay with Stonn]]. Satisfied, Spock leaves T'Pring to her lover, warning him that [[WantingIsBetterThanHaving wanting may be better than having]], and returns to the ''Enterprise'' to turn himself in for murder.

But wait! Turns out, [[NotQuiteDead Kirk isn't dead!]] Yes, the substance [=McCoy=] gave him during the battle was actually some AppliedPhlebotinum which allowed Kirk to simulate death. The episode ends with Spock [[NotSoStoic barely catching himself from having a joygasm over Kirk's survival]], and Kirk and [=McCoy=] having a good tease over it. Meanwhile, T'Pau covers for Kirk's shenanigans, saving him from another court martial.

* AccidentalHug [=/=] TheUnHug: Overjoyed that Kirk wasn't KilledOffForReal, Spock grabs him by the arms... and quickly attempts to pretend he didn't when he notices that Chapel and [=McCoy=] are watching.
* ActOfTrueLove:
** Kirk sacrifices his career to save Spock. He gets it back, [[LikeYouWouldReallyDoIt of course]], but he didn't know that that would happen.
** In return, Spock humiliates himself in front of [[GrandeDame T'Pau]], the woman Kirk referred to as "all of Vulcan wrapped up in one package", by begging her to keep Kirk out of the ''kal-i-fee''. T'Pau throws it back in his face with a few insults about his humanness, and it still isn't enough to stop him. As much as he fears breaking the taboo against emotions in front of his people, he fears more that Kirk will die if he doesn't attempt to save him.
* AFriendInNeed: Kirk is patient with Spock's antics while under the ''ponn farr''. Later, he sacrifices his command to save him (and almost sacrifices his life). His reason why? "He's my friend."
* ArrangedMarriage: Spock and T'Pring.
* AwLookTheyReallyDoLoveEachOther: For all their sparring, [=McCoy=] proves that he and Spock truly are VitriolicBestBuds; when Spock asks him to accompany him to the ''pon farr'', [=McCoy=] simply states he would be honored, without any attendant snark.
* BitchInSheepsClothing: T'Pring. Granted, being married to a guy who you haven't seen in years would be potentially trying, but Vulcans have come to expect it. She is willing to force a fight between two best friends, one of whom is completely ignorant of what she is asking and the other of whom possibly has no more control over the ArrangedMarriage than she does.
* BlatantLies: Spock's reaction at the end of the episode. He was ''not'' "on the verge of... an emotional display"; he was simply pleased that Starfleet had not lost one of its finest officers. [=McCoy=] {{lampshade}}s how poorly the Vulcan's lies stand up.
-->'''[=McCoy=]''': Of course, Mr. Spock, [[SarcasmMode your reaction was quite logical]]. ...[[{{Not}} In a pig's eye!]]
* BottledHeroicResolve: Subverted. Kirk becomes exhausted while duelling the deranged Spock, and [=McCoy=] calls a time-out to inject him with something that will give him a fighting chance. A TechnoBabble explanation is provided it'll help Kirk use the oxygen in his blood more efficiently, since the atmosphere on Vulcan is thin by Earth standards. Of course, [=McCoy=] has actually slipped him a mickey, giving him a sedative that will simulate sudden death and make it appear that Spock has won the battle.
* {{Bowdlerize}}: The German dub infamously completely changed the plot to remove all sexual references, as over there, they think ''Star Trek'' is a kids' show. As a result, the entire episode plays out as if the whole thing was just a dream, which is kind of a screw to the audience if you've ever seen the episode as it was in America. In the 90s, a correct dub of the episode was finally released.
* ContinuityNod: Chapel's attraction to Spock from "[[Recap/StarTrekS1E4TheNakedTime The Naked Time]]" is brought up again. Apparently she's been constantly trying to raise his interest ever since, much to Bones' amusement.
* CoolOldLady: T'Pau is an ''archetype''. Few television shows ''ever'' have portrayed a woman of such advanced age (according to canon, she's 145, with Celia herself 70 at the time) in such an exalted position of power -- aside from QueenVicky or [[HMTheQueen her descendants]]. You're looking at the gal who once told the Federation Council what they could do with their invitation, and who with a simple phone call to Starfleet Command saved Kirk from getting busted down to Spaceman Third Class for his hijacking of the Big E to take Spock home. ''All of Vulcan in one package.''
* DeathFakedForYou: [=McCoy=] [[SlippingAMickey gives Kirk a neural paralyzer]] to prevent an actual death.
* DeathWorld: Vulcan is quite inhospitable to humans, to the point that "hot as Vulcan" has become a common saying.
* DidNotSeeThatComing: [=McCoy=]. T'Pring never mentioned him when explaining her plan to Spock, and Spock invited him as a friend, not as backup. Nonetheless, he's single-handedly responsible for the episode's HappyEnding.
* DontMakeMeDestroyYou: Not directed at Kirk himself, but on the verge of losing his sanity Spock practically begs T'Pau not to let him go through with the fight, as he does not want to kill his best friend.
* DutchAngle: Canted camera work appears soon after the PowerTrio arrive for the wedding, focusing on the Vulcans. It serves to show just how unbalanced Vulcans in ''ponn farr'' become.
* DueToTheDead: Me TV rescheduled this episode to play in the wake of Leonard Nimoy's death. While the previously scheduled [[Recap/StarTrekS1E24ThisSideOfParadise "This Side of Paradise"]] did also focus on Spock, this episode explored his character just a bit more.
* EasilyForgiven: In spite of Spock's attempt to murder him, Kirk is back to their [[HeterosexualLifePartners regular]] [[TheNotLoveInterest relationship]] by the end of the episode.
* EngagementChallenge: Well, sort of. A Vulcan bride can make her husband-to-be fight a challenger to win her, a remnant of the past when Vulcan men fought each other for mates before the whole process became cloaked in ritual and tradition.
* ExactWords[=/=]LoopholeAbuse: Spock attempts to use this on [=McCoy=], saying that the Captain told him to "report to Sick Bay", and now that he has done so, he intends to leave. [[RealityEnsues [=McCoy=] doesn't buy it, countering that he (obviously) has orders to give Spock a medical checkup.]]
* FirstNameBasis:
** [[HospitalHottie Chapel]] encourages it with Spock, who actually goes with it.
** Spock calls Kirk by his first name upon seeing that he's NotQuiteDead.
* ForgetsToEat: According to Kirk, one of Spock's habits when in "one of his contemplative phases" is not eating.
* GrandeDame: T'Pau, a clan elder in Spock's family. T'Pau is a deeply commanding figure of respect with unquestioned authority. For instance, she makes sure Kirk does not get into trouble diverting to Vulcan to get Spock for the ceremony.
* HalfBreedDiscrimination: Of the verbal variety. When Spock begs T'Pau to keep Kirk out of the combat, she responds, "It is said thy Vulcan blood is thin. Art thee Vulcan, or art thee human?"
* HeroicBSOD: Spock suffers one of these after the ''koon-ut-kalifee''.
* IOweYouMyLife: Kirk says that Spock has saved his life a dozen times over when deciding to disobey orders.
* IndyPloy: [=McCoy=] improvises a way to keep Kirk and Spock from killing each other pretty much on the spot and with no opportunity to discuss it with anyone else. As an Unspoken Plan, it naturally [[UnspokenPlanGuarantee succeeds]].
* LeaveMeAlone:
** Spock snarls this when Uhura calls his quarters with a message, smashing the computer terminal while doing so.
** Before that, he chases Nurse Chapel out of his quarters, hurling the soup she made for him against the wall.
* LettingTheAirOutOfTheBand: When Spock realises he's smiling and shuts down all expression, the swelling music grinds to a very awkward halt.
* LivingLegend: Spock, according to T'Pring during her explanation of why she didn't want him.
* [[ManipulativeBastard Manipulative Bitch]]: T'Pring.
* MateOrDie: Bones speculates that this is the price Vulcans pay for keeping their emotions bottled up the rest of the time. Ultimately {{Subverted}}, however, as (seemingly) killing Kirk snaps Spock out of it.
* MindlinkMates: Spock had a mindlink placed in him as part of an ArrangedMarriage when he was a child. This mindlink was suspiciously easily overcome.
* MoreDeadlyThanTheMale: While Stonn would presumably have thrown his all into the ''kal-i-fee'', his girlfriend proves to be the far greater danger.
* MyGodWhatHaveIDone: Spock, believing that he has murdered Kirk, loses his will to live.
* NotQuiteDead: Kirk.
* NotSoStoic: A famous example, when Spock sees Kirk alive and well.
* OhCrap:
** Kirk, when he is in Spock's quarters and realizes that Spock has been holding a knife in his trembling hand for their entire conversation.
** When Kirk realizes his fight with Spock is one to the death.
** Spock's reaction when he realizes he's just been emotional in front of Kirk, Christine Chapel, and [=McCoy=]. Unlike the others, it's PlayedForLaughs.
* OOCIsSeriousBusiness: As in, "life-and-death" serious. Spock loses his temper on a number of occasions and completely forgets about having changed course, despite having immense self-control and an encyclopedic memory.
* PleaseSpareHimMyLiege: Spock begs T'Pau to block Kirk from the ''Kal-i-fee''. She throws it back in his face with a few insults about his [[HalfBreedDiscrimination humanness]].
--> T'Pau... thee has the power. I plead with thee. I beg....
* PoorCommunicationKills:
** Spock would literally rather die than have the problem explained to Starfleet Command. This is apparently true of all Vulcans at this point in history.
** It's also possible that Kirk could've explained things to Komack in a way that would've gotten him permission to go to Vulcan without letting too much slip. Kirk even had his Chief Medical Officer's statement that Spock would die if he didn't return to Vulcan, and didn't bother to mention it to the Admiral.
** Poor communication also almost killed Kirk in this episode. Would it have hurt T'Pau to tell him that the fight was a [[InvoluntaryBattletotheDeath death match]] ''before'' he signed up?
* PromotionToOpeningTitles: Dear old [=DeForest=] Kelley as Dr [=McCoy=] in this second season opener. At last, the whole PowerTrio is in the opening credits.
* RedSkyTakeWarning: Vulcan's sky is scarlet when the PowerTrio arrive for the wedding, almost as though foreshadowing what's going to happen.
* RememberTheNewGuy: Chekov is introduced as already an established crew member, though there's some odd close-up camerawork to make sure we know he's not just another one-off co-pilot for Sulu.
* ReportsOfMyDeathWereGreatlyExaggerated: Upon returning to the ''Enterprise'', Spock starts detailing his plans to leave Starfleet when Kirk suddenly walks in.
* RunawayBride: T'Pring, in a way.
* SeriesContinuityError: T'Pau is shown to speak fluent English in the [[Series/StarTrekEnterprise prequel series]].
* SlippingAMickey: [=McCoy=] gives Kirk a shot, saying that it would help Kirk breathe the thinner Vulcan air. He really gave Kirk a neural paralyzer that made it look like he was dead.
* StealthHiBye: As Spock is explaining how he's going to resign his commission and turn himself in for Kirk's murder, Kirk walks up behind him. Dr. [=McCoy=] and Nurse Chapel can't keep the grins off their faces.
* TheBeCarefulSpeech: [=McCoy=] tells Kirk to "be careful" as he enters the second round against Spock.
-->'''Kirk''': [[DeadpanSnarker Sound medical advice.]]
* TheTalk: Spock is forced to explain Vulcan mating habits to Kirk partway through the episode.
* ThroughHisStomach: Christine Chapel shows her concern for Spock by bringing him some Vulcan food.
* TooImportantToWalk: T'Pau is carried to Spock's wedding in a sedan chair.
* UnwantedSpouse: Spock and T'Pring for each other.
* WantingIsBetterThanHaving: Spock warns Stonn that he may find that "having is not so pleasing a thing, after all, as wanting. It is not logical, but it is often true."
* WeddingDay: Well, kind of.
* WomanScorned: T'Pring and Spock were bonded at seven. They should have been mated at eighteen - that's right, T'Pring has been waiting ''twenty years'' for her wedding night - instead Spock humiliates her by putting off their consummation and, according to 'Vulcan's Glory' tries to buy her off with money. Is it any wonder she wants him dead?
* XanatosGambit: Even if Kirk had refused the challenge, or Spock had won but still been willing to go through with marrying her, her husband's Starfleet position would mean that he'd be gone most of the time, leaving her free to have an affair with Stonn in his absence; at a minimum, she's no worse off than she was to start with. Spock himself acknowledges the logic of her plan, even while personally repelled by it.
* YeOldeButcheredEnglish: Writer Creator/TheodoreSturgeon apparently wanted to show that the Vulcan language, or at least an older form of it, had separate second-person singular and plural forms (as French does with "tu" and "vous"). They showed this by using the archaic second-person familiar pronoun "thee" for "you". But T'Pau, the one character to use these formal archaisms, used "thee" even when "thou" would have been the correct word. Even if Vulcan used the same word for both pronouns (as modern English does with "you"), the translator should have been programmed to recognize the difference between subjective and objective pronouns. As it was, formal Vulcan as rendered by Celia Lovsky sounded more like Quaker 'plain speech'. If thou art the subject of a sentence then the object of the sentence wouldst be thee.
* YouAreInCommandNow: A somewhat unusual example. Blood-fever affected Spock apparently kills the captain. After coming to his senses, Spock finds himself in command, as noted by Dr. [=McCoy=].
-->'''[=McCoy=]''': As strange as it may seem, Mister Spock, you're in command now. Any orders?
-->'''Spock''': Yes. I'll follow you up in a few minutes. You will instruct Mister Chekov to plot a course for the nearest Starbase where I must surrender myself to the authorities.
* YouCalledMeXItMustBeSerious: Probably the most famous time Spock has ever foregone Kirk's title for his first name. It would be hard to think of a situation that warranted it more.
-->'''Spock''': Captain... ''Jim!''