[[caption-width-right:350:''[[Music/EricCarmen "Alllllll byyyyyyy myyyyyyyseeeeeeelf..."]]'']]
The planet of Gideon has refused anything to do with the United Federation of Planets until recently. The council has agreed to allow a delegation of one...one Captain James T. Kirk. Kirk has himself beamed down to the planet only to find himself beamed aboard his own starship, sans crew. Where is everybody? Kirk searches everywhere, hails everyone he can think of. His voice over the intercom reverberates off the walls of empty rooms. Kirk searches until he finds a rather dippy blonde in sparkly blue and purple PJ's dancing by herself in the corridors. Oh, Donna! No, actually [[GirlOfTheWeek her name is Odona.]] She's not sure where she's from, just that it was so crowded it made a [[Music/TheWho Who]] concert look tranquil. It isn't long before Kirk is BoldlyComing. (You can bet they didn't go into that room to play Parcheesi!) Spock, meanwhile, is playing bureaucratic ping-pong for permission to search for the missing captain.
!!Tropes for this episode include:
* AbusiveParent: Subversion. Hodin is quite willing to make his daughter suffer and die from meningitis. However, she volunteered to do this for [[HeroicSacrifice the good of the many.]]
* AdultFear: Kirk wakes up on an empty ''Enterprise'', all the crew members with whose safety he has been entrusted gone without a trace or any clue to what happened to them.
* ArtisticLicenseBiology: Leaving aside the fact that it's impossible for a planet to be "germ free"...if Gideon were completely germ free as said, it wouldn't result in people living very long lives. It would result in a population that had zero immunity...also leaving aside the fact that complex life can only exist in symbiosis with single celled life (a typical human contains 3 time as many bacteria cells as human cells - most of which are beneficial to us). The entire population would be wiped out as soon as any pathogen were introduced. It wouldn't take an exotic, deadly illness like Kirk carried to do it. It would happen the first time they came in contact with alien visitors.
* AssInAmbassador: Hodin is quite good at prolonging a crisis and insulting Scotty while he's at it.
* BerserkButton: Do not even hint to Scotty that his equipment is faulty. (Mind out of the gutter! They're talking about the transporter!)
* BrokenAesop: Genocide is ok when the world is overpopulated and people are unhappy about being so dang healthy all the time.
** Kirk does try to convince them to use birth control instead, but contraception is apparently against their religion.
* CannotKeepASecret: Someone in Starfleet, since the Gideon government has access to a lot of useful information about the Enterprise and her Captain.
* ComplexityAddiction: The planet needs Kirk's blood to introduce a disease to basically start a plague that will kill off a large percentage of their population. Rather than get this in a more mundane way (like subjecting him to a medical exam on the planet), they go to a huge amount of trouble (and space) to build an entire fake Enterprise, and then still just take a blood sample when he's unconscious. Supposedly, they need him to provide a constant supply of the virus, as they apparently can't just culture it or something.
* CurseCutShort: Scotty bites his tongue before insulting the Gideon council before begrudgingly referring to them as "gentlemen".
* DepopulationBomb: Kirk is kidnapped by a vastly overpopulated planet who wants to use germs in his blood to drop a Depopulation Bomb on ''themselves''.
* DistractedByTheSexy: Kirk is going mad with worry until Odona comes along. One germ swapping kiss followed by an off scene lay, and he's back to worrying about them.
* DramaticallyMissingThePoint: Instead of using the negotiations with the Federation to prepare a colonization plan, the government of Gideon decide to use the negotiator's deadly germs.
* DyingDeclarationOfLove: Odona makes one to Kirk. Her passions cool when she realize she's not going to die after all, but has the potential to make many others sick so people can get to dying so everyone can be happy.
* IllGirl: Odona seeks to become one and succeeds.
* InnerMonologue: Instead of the usual CaptainsLog, we hear Kirk's reverberating thoughts about what may have happened to his crew. And why does his arm hurt?
* LiteraryAllusionTitle: A mix of two Biblical myths. Cain killed his brother, reducing the known world population to three and was forever marked for it. Gideon used arbitrary methods to reduce the size of his army.
* MakeAnExampleOfThem: Partly inverted, since the message isnít about punishment, but about salvation.
-->'''Hodin:''' No, her death at so young an age will let the people know for certain that our lifecycle can be changed. It's the symbol that'll bring forth [[HeroicSacrifice the dedicated young volunteers]]. [[RestartTheWorld The serum in their new blood will change Gideon, and it will once more be the paradise it was.]]
* MetaphoricallyTrue: The Gideons never said their planet was a Paradise. They said it ''used'' to be one. They just said the atmosphere was pristine and no one was ever sick. That's what's making the place unbearable.
* ObstructiveBureaucrat: Admiral Fitzerald, the rest of Starfleet Command and the Federationís Bureau of Planetary Treaties.
* OntologicalMystery: Kirk beamed from his ship...to his ship...or is it his ship?
* OutOfCharacterMoment: Perhaps George F. Slavin and Stanley Adams didnít need to know TheKirk himself survived a [[Recap/StarTrekS1E13TheConscienceOfTheKing similar massacre]], but they should have known [[TakeAThirdOption he doesnít so easily accept no-win scenarios]].
* PlanetOfHats: Kirk is kidnapped by a race whose universal pro-life tendencies had lead to horrible overpopulation, to the point that they tried to start a pandemic with germs from Kirk (who had been exposed to Vegan choreomeningitis in the past). Kirk flaunts Humanity's "freedom" hat by stating categorically that he does not want to stay on this planet as their own hemlock dispenser and instead suggests using one of many forms of birth control the Federation had to offer. (Um...you remembered to use one on Odona, right, Kirk?)
* PlotHole: [[WorfHadTheFlu Did the computer have a throat infection this week?]] Trying to consult its databanks and the record tapes as usual would have been more useful than looking at windows.
* PopulationControl: The planet's failure to deal with this led to ridiculously extreme overcrowding (though no problems with health or resources, apparently).
* PrinciplesZealot: People of Gideons are against contraception because love and life is sacred, so bringing death and sickness is the only acceptable solution.
* SendInTheSearchTeam: Spock wants to do this to find Kirk, but [[ObstructiveBureaucrat neither Gideon or the Federation]] will give permission to do so. He decides ScrewTheRulesImDoingWhatsRight and beams down to go in search of Captain Kirk himself.
* TemptingFate: When Spock decides he will look for Kirk by himself (asking another crew member to accompany him would just get him in further trouble with Starfleet) he announces "I will not be long." Scotty points out that Kirk said the same thing.
* WellIntentionedExtremist: Gideons are ready to use [[UtopiaJustifiestheMeans lethal and painful methods to restore their paradise]].
* WeWillHaveEuthanasiaInTheFuture: An extremely overpopulated world is trying to set up a voluntary suicide system, starting by infecting the leader's daughter with a disease. You'd think they find a better way to euthanize people than some painful, (relatively) drawn out disease. Maybe they're all masochists? Odona certainly seems to have a fascination for pain...
** As part of the religious parallels being drawn with the culture, they refuse to consider contraception or to ''directly'' take another's life. But manipulating events to cause people to become ill and die "naturally", that's just fine!
* WouldBeRudeToSayGenocide: Self inflicted genocide, no less. Because of the horrible overpopulation and that horrible healthyness, you see. But no birth control, because we love life so much, you know. So instead of ordering us some starships, we would much prefer your painful disease now.
* TheXOfY: The Mark Of Gideon