[[caption-width-right:350:[[FanService Ohhh myyyy.]]]]

->''"I'll never lose you. Never."''
-->-- '''Kirk''', revealing his... ''[[CargoShip fondness]]''... for the ''Enterprise''

The ''Enterprise'' has arrived at the ice planet Psi 2000 to document its impending collapse. Spock and [[RedShirt some other loser]] beam down in Hazmat suits to investigate why a laboratory on the planet shows no life signs: turns out, everybody froze to death because someone left the door open and nobody cared enough to correct that. While Spock is investigating the corpses, his companion [[TooDumbToLive unwisely]] removes his glove to scratch his nose, allowing a strange red fluid to drip onto his hand.

Back on board the ''Enterprise,'' the RedShirt starts acting strangely, in turns belligerent and depressed. He gets into a fight with Sulu and a guy named Lt. Kevin Thomas Riley, brandishes a dinner knife at them, and mildly injures himself. However, when [=McCoy=] operates on him, he dies, seemingly losing his will to live. [=McCoy=] is perplexed, as the victim was in good health and was previously known as a strong-willed individual. The reason for his odd behavior soon becomes apparent: he carried a virus that removes inhibitions (and makes one extremely sweaty, incidentally).

Chaos engulfs the ship as the virus spreads: crew members act carelessly, laughing maniacs run around the halls painting creepy messages in red paint, Sulu menaces passersby with a fencing sword, and Spock enters a crippling depression. Worst of all, Riley has locked himself in the engine room, hijacking the PA system to make bizarre announcements and advise women on hair and makeup styles, stranding the ship just as the planet is breaking up, threatening the ''Enterprise.'' Kirk and Scotty try to break into the engine room while [=McCoy=] cooks up a vaccine. However, by the time Scotty gets the door open, it's revealed that the engines were stopped completely and that restarting them would take more time than the planet has. Desperate, Kirk orders Scotty to... [[{{Technobabble}} do something involving matter/antimatter annihilation]] to get the Enterprise out of the way. Scotty cries that it only has a [[MillionToOneChance 1-in-10,000 chance]] of not blowing them to smithereens (so, naturally, it will work perfectly), but he needs Spock's help. Kirk tries to [[GetAHoldOfYourSelfMan slap Spock out of his funk]], but Spock only recovers when Kirk empathizes with him under the virus's influence and reveals the heavy burden of being Captain of the ''Enterprise''--contrary to popular belief, ''you can never get laid,'' at least not with crew members. [=McCoy=] cures the crew and the ship escapes, but with a strange side-effect: it travels about three days backwards in time, in the series' first instance of time travel.

[[Series/StarTrekTheNextGeneration TNG]] [[strike: ripped off]] simply ''[[SarcasmMode revisited]]'' this scenario in "[[Recap/StarTrekTheNextGenerationS1E2TheNakedNow The Naked Now]]." ...'''[[RecycledScript just]]''' revisited.

* AnguishedDeclarationOfLove: Nurse Chapel makes one for Spock.
* BrokenTears: Spock loses all control over his emotions.
* ClothingDamage: A bizarre instance; it's already been established that hyposprays can be used to inject people through their clothing, and even if they did need to be used on bare skin, [=McCoy=] could have just injected Kirk on the neck (which isn't covered by his uniform), or have him roll up his sleeve. Instead, for absolutely no explicable reason, [=McCoy=] tears open Kirk's uniform at the shoulder in order to inject him.
* CurtainClothing: The environmental suits were made from Art Deco shower curtains.
* CuteButCacophonic: Lt. Riley. "I'll take you hoooome Kathleeeeeeen!"
* DeathByDespair: A RedShirt tries to commit suicide, is stopped before he seriously hurt himself, then dies anyway because he can't summon the will to fight off the minor infection of the wound.
* DecontaminationChamber: The transporter room is shown to have the ability to decontaminate the outside of isolation suits with some sort(s) of radiation. Of course the sort of radiation that would do that would also, at the least, damage the skin of the people in the suits unless the suits blocked the rays...and unfortunately the idiot who beamed down with Spock had taken off a glove, been contaminated, and then put the glove back on--thereby making sure the rays would do nothing (not that they'd have done anything against an infection within someone's body anyway).
* DeniedFoodAsPunishment: Riley tells Uhura she can't have ice cream because she interrupted his song.
* DrivenToSuicide: Joe Tormolen, who laments that humanity doesn't belong in space, stabs himself, and then despite receiving prompt medical attention, [[DeathByDespair loses the will to live.]]
* DrunkenSong: Riley [[DreadfulMusician sings]] an "ancient Irish favorite."
* EarlyInstallmentWeirdness:
** {{Lampshaded}}. Lt. Riley claims that Sulu's interest in botany in [[Recap/StarTrekS1E1TheManTrap "The Man Trap"]] was one of his weekly fads. This week it's fencing.
** They're still working through Spock's mannerisms by this time. When he nerve pinches Sulu, he says to the security guards, "Take D'Artagnan here to Sickbay."
** The opening CaptainsLog doesn't include a Stardate, though the subsequent log after the opening credits does.
* EverybodyMustGetStoned: A disease makes everyone get progressively drunker.
* GetAholdOfYourselfMan: Kirk attempts to slap Spock back into a steady state of mind. All it does is get Spock mad enough to slap him back, with enough force that he goes flying across the table.
* GettingCrapPastTheRadar: Uhura's quip when Sulu grabs her.
-->'''Sulu:''' Aha!, fair maiden!\\
'''Uhura:''' Sorry, neither.
* GracefulLoser: Riley has made a number of announcements over the ship's PA system, including a formal dance in the ship's bowling alley. After going through considerable effort to force their way into Engineering, Kirk leads the charge with Scotty and a pair of Security crewmen. Riley looks up from the chair and dryly observes, "No dance tonight."
* HollywoodToneDeaf: Kirk might not mind Riley's singing so much if it had somewhat less enthusiasm and a little more musical talent.
* TheHyena: The disease turns a few people into this.
* InelegantBlubbering: Spock when he gets affected.
* LoveIsInTheAir: The disease makes people lose their inhibitions, so many of the afflicted find themselves acting more amorous than usual.
* MadnessMantra: Spock tries to ward off the effects of the disease by repeating "I am in control of my emotions" and reciting multiplication tables.
* MillionToOneChance: Scotty gives the odds of successfully cold-starting the engines without blowing themselves up as 1 in 10,000--and that's ''with'' a supercomputer and weeks to calculate the formula. Fortunately, Spock is better than a supercomputer, if they can get him to stop crying long enough to focus.
* MurderWater: Contrary to the episode synopsis you just read, the episode itself doesn't have the cause to be a virus--that was the retcon used in the "revisiting" to cover the fact that the central premise of "The Naked Time" fell squarely into ScienceMarchesOn: polywater, a kind of high-viscosity, low-freezing point water that would tend to make other water into its own type. It's not actually ''sentient,'' but it is extremely dangerous, can move in ways that should be impossible, and is (a type of) water.
--> '''[=McCoy=]'''. It's water! Somehow on this planet, water's changed to a complex chain of molecules. That's how we missed it. It passed from man to man through perspiration. Once in the bloodstream, it acts like alcohol... depresses the centers of judgment, self-control.
* OhNoNotAgain: Kirk's reaction to Lt. Riley's announcement that he is going to sing another [[HollywoodToneDeaf rendition]] of "I'll Take You Home Kathleen."
-->'''Riley:''' And now, crew, I will render "Kathleen"... ooonnne moooore tiiiimme!
-->'''Kirk:''' ''[muttered]'' Please, not again.
* {{Oireland}}: Riley goes über-Irish while drunk.
--> '''Riley.''' You know what Joe's mistake was? He wasn't born an Irishman.
* [[SpaceDoesNotWorkThatWay Orbits Do Not Work That Way]]: There is no ice-planet's reason in hell that the ''Enterprise'' needs to "spiral down" as the doomed planet shrinks. Are they connected by fishing line or something?
* ThePlague: The disease is apparently non-fatal, but is highly contagious and, in both episodes, adversely affects the crew in the midst of a disaster which could destroy the ship.
* PlotHole: Dr. [=McCoy=], a front-line medical worker, never succumbs to the disease--pretty impressive considering that it manages to afflict his head nurse.
* SchmuckBait: What exactly did Kirk expect to happen when he touched the end of Sulu's sword?. (There are no euphemisms in the previous sentence, but don't let that stop your imagination.)
* ScottyTime: "[[MemeticMutation I cannae change the laws of physics!]] I've got to have thirty minutes!" In this case, it's actually not an inflation, but the faster alternative of trying to cold-start the ''Enterprise's'' engines is way too risky for Scotty's skill level.
* SequelHook: Spock accidentally invents time travel, with Kirk noting that it could be pretty interesting to try again some day.
* ShirtlessScene: Sulu gets one. [[Creator/GeorgeTakei Oh,]] [[CatchPhrase my!]]
* TooDumbToLive: Taking off your glove, getting some weird liquid on your hand, and then rubbing your nose? If the virus hadn't gotten him, this guy doubtlessly would have found some other way to kill himself in a few days.
* WorldOfHam: Everybody under the influence of the virus starts gobbling up the scenery, nobody better than Riley, though.