[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/ds9s2_01.jpg]]
[[caption-width-right:350:Kira is seeing double.]]
Kira and Bashir have an unusually rough trip through the wormhole on their way back to [=DS9=], and emerge to find the station nowhere in sight. Things get even stranger when they are boarded by Klingons who are initially hostile but immediately become downright apologetic when they see Kira.

They discover that they are in the MirrorUniverse [[Recap/StarTrekS2E4MirrorMirror that Kirk and his crew discovered a century earlier]]. In this alternate universe, Kirk did successfully persuade Mirror Spock to reform the Terran Empire, but this made the Terrans easy conquest for TheAlliance, a coalition of Bajorans, Cardassians, and Klingons. Deep Space 9 is still Terok Nor, under the command of Intendant Kira Nerys and First Officer Garak, and the Terrans are enslaved. Bashir is assigned to labor in ore processing under the watchful eye of the alternate Odo, but Intendant Kira takes an interest in her counterpart and spares her the same fate.

Intendant Kira is willing to entertain the idea of letting Kira return to the prime universe and gives her free run of the station, but for a lax bodyguard. Kira tries to get help from the Mirror Quark, but he is found out and executed, and she has less success with the Mirror Sisko, who was able to charm his way up to being Intendant Kira's enforcer in the sector. The Mirror Garak is willing to help her, if she'll help him overthrow Intendant Kira so he can take command. Bashir tries to get assistance from the Mirror O'Brien, but he's too cowed to offer any.

As the two Kiras attend a party with Sisko's crew, an emergency down in ore processing creates an opening for Bashir to kill Mirror Odo and escape. O'Brien agrees to help him and asks to return to the prime universe with him. They're caught and brought before Intendant Kira, who questions why O'Brien, a high-ranking slave, would betray them. O'Brien explains that he's heard Bashir's stories of the prime universe, and it inspired him to try for something better than this. Inspired by O'Brien's words, Sisko and his crew turn on Intendant Kira and flee the station. O'Brien joins Sisko's crew rather than flee the universe, while Kira and Bashir take their runabout back through the wormhole, their original {{Technobabble}} hiccup that caused them to enter the mirror universe still working to bring them back home.

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!!Tropes

* AffablyEvil: Intendant Kira is very friendly and personable. Although she tends to avoid violence when possible, she'll still enforce the brutal Alliance and casually order executions.
* AliceAllusion: When Sisko asks where Kira and Bashir have been after they return, Kira replies "Through the looking glass, Commander." (This would, of course, later be the title of [[Recap/StarTrekDeepSpaceNineS03E19ThroughTheLookingGlass the next]] Mirror Universe episode.)
* TheAlliance: Between the Klingons and the Cardassians, with Bajor having recently joined.
* AmbiguousSituation: Is Bashir hitting on Kira, or is he really just trying to get to know her? We don't find out.
* AnyoneCanDie: Because the creators didn't originally intend to write any more Mirror Universe stories, this trope is in full effect, with the counterparts of Quark and Odo being killed off quite casually.
* BadBoss: Mirror Odo, with a side-order of MeanBoss too.
* BittersweetEnding: Although the main characters manage to escape and inspire a human rebellion, TheEmpire is still in charge in the mirror universe and mirror Quark is executed for helping humans escape.
* ButtMonkey: No surprise that a MirrorUniverse version of O'Brien would also suffer this. He's overworked by both Odo and Sisko (most slaves only have one master to answer to) and his warnings of a thorium leak go unheeded until everything goes to hell.
* ChekhovsLecture: Mirror O'Brien repeatedly warns of an impending thorium leak in ore processing, but [[CassandraTruth nobody cares to listen]]. By the end of the episode, a serious malfunction occurs.
* ContrivedCoincidence: Kira and Odo being on the Mirror Terok Nor makes sense, but the Mirror versions of Sisko, Quark, and O'Brien all being there too is extremely unlikely, given that the circumstances that lead them there in the normal continuity don't exist in the Mirror Universe. Not to mention the very existence of Terok Nor, which is designed in the exact same way as the regular counterpart, in the first place.
* CrapsackWorld: Despite Kirk indeed managing to convince mirror Spock to reform the Terran Empire for the better, that only made them weak enough for the Cardassian/Klingon/Bajoran alliance to conquer them, resulting in a world where [[TheBadGuyWins the bad guy won]] and humans are their slaves.
* CrazyPrepared: The Mirror Universe was so scared by Kirk's actions that any figure of authority is to keep an eye out for any sign of a crossover.
* DeadlyEuphemism: Mirror Garak says that Intendant Kira will be "gone" by tomorrow. When Kira doesn't clue in, he immediately lampshades his use of a euphemism to get his point across.
* DepravedBisexual: Intendant Kira is heavily implied to have a sexual relationship with the Mirror Sisko, is attracted to her own alternate self, and is almost giddy at the thought of there being another Sisko so she could have one on each arm. She also spends the episode walking around in a tight black uniform that shows off her curves.
* DistantSequel: This episode takes place 103 years after "[[Recap/StarTrekS2E4MirrorMirror Mirror, Mirror]]".
* DutchAngle: Seems the Mirror Universe runs on this.
* EmbarrassingNickname: Mirror O'Brien doesn't like being called "Smiley," a name that [[IronicNickname doesn't fit his rather beaten-down disposition]] and which Mirror Sisko insists on using [[MaliciousMisnaming despite (or because of) his dislike]].
* EvenEvilHasLovedOnes: Massively Downplayed. Mirror Kira is horrified at Odo's death, which may be part of why she's much more overtly evil in subsequent appearances, however in this case it's more that she's lost an efficient, loyal, and especially cruel slavedriver than a loved one.
* EvenEvilHasStandards: Subverted. Mirror Kira doesn't like violence and reins her minions' more violent impulses in. Of course, Mirror Kira herself is more than happy to murder people or order people killed in every single one of her subsequent appearances, indicating she only dislikes Violence that isn't on ''her terms''.
* EvilCounterpart: Played straight with Mirror Odo, Garak and Kira, Zig-zagged with Mirror Sisko, and averted with Mirror O'Brien and Quark.
* EvilIsHammy: Mirror Kira is easily the worst offender. Sisko is less heroic than his normal counterpart and much more hammy.
* {{Fanservice}}: Tight leather get-ups, bath scenes, swanky dresses, LesYay out the wazoo... someone in the writers room clearly enjoyed Kira.
* HappyEndingOverride: The original appearance of the Mirror Universe ended on a hopeful note, with mirror-Spock seriously considering Kirk's call to bring down the Terran Empire and replace it with something more enlightened. A century later, the Terran Empire is gone... replaced by a repressive Klingon/Cardassian/Bajoran regime that has enslaved humanity.
* IgnorantOfTheirOwnIgnorance: Bashir had heard of the original crossover, but Kira hadn't even heard of Kirk before these events. Likely justified as Kira hasn't shown an interest in wider galactic history and none of her Starfleet colleagues would have had a reason to talk about one incident over a century ago.
* IronicNickname: Mirror O'Brien was given the nickname "Smiley" by Mirror Sisko. He's very unhappy and never smiles.
* KillAndReplace: Part of Mirror Garak's plan is to kill Mirror Kira so that our Kira can replace her.
* KilledOffForReal: Mirror Odo gets blasted apart with a phaser and Mirror Quark is executed, and they don't appear in subsequent Mirror Universe stories.
* LudicrousGibs: This episode displays the effect of a phaser on a changeling. Odo explodes into a gooey mess.
* MakeAnExampleOfThem: Mirror Garak wants to do this to a Terran slave who tries to escape, but Mirror Kira considers his methods too brutal. After Bashir kills Mirror Odo, Kira gives Garak permission to do this to the Terrans.
* MercyKill: After getting a confession from Mirror Quark, Mirror Kira has him put to a quick death.
* MirrorCharacter: Kira's evil Mirror counterpart is remarkably similar to her Prime universe nemesis Gul Dukat, being a ruthless oppressor who justifies herself by claiming she's the lesser evil compared to anyone else who'd take the job, whose pretenses of being a kinder, gentler tyrant quickly go out the window when things don't go her way, and who seems to have a thing for claiming consorts from the slave populace that she's in charge of oppressing.
* NiceJobBreakingItHero: Kirk convincing Spock to try and reform the Terran Empire allowed the Klingons and the Cardassians to conquer them and enslave mankind (and presumably the rest of the Empire's subjects). Thanks, Kirk.
* NoSenseOfHumor: Mirror Odo's "Rule of Obedience" #14: "No jokes."
* NoSenseOfPersonalSpace: On first seeing Kira, Mirror Sisko tries stroking her face. Then he tries kissing her.
* NoTimeToExplain: Kira telling Bashir that he's in danger.
* PlanetTerra: As with the original ''Star Trek'', Earth is known as Terra here and humans as Terrans (this time as a FantasticSlur).
* OOCIsSeriousBusiness: Kira and Bashir are confused when the Klingon warriors who board their spacecraft back off with groveling apologies the moment they see Kira, mistaking her for the Intendent.
* PurpleIsPowerful: Both Kiras get matching purple outfits to wear for a party.
* SadisticChoice: Kira can trust Garak to overthrow Intendant Kira and assume her place for a time before arrangements can be made to get her off-station so she can return the prime universe, or Garak can have Bashir killed.
* SayMyName: When Mirror Garak shows up to arrest Mirror Quark:
--> "QUAAAAARRRRRK!!!"
* ScrewYourself: Intendant Kira more or less directly tells Kira she wants to sleep with her, and her sexual interest is self-evident in their interactions otherwise. Mirror Garak implies this is a result of LonelyAtTheTop, as the Mirror Kira sees in her doppelganger the perfect companion and confidante she can trust.
* SequelEpisode: To the [[Series/StarTrekTheOriginalSeries original series]] episode "[[Recap/StarTrekS2E4MirrorMirror Mirror, Mirror]]".
* ShutUpHannibal: Mirror O'Brien gives a powerful one to Intendant Kira when she asks why he would throw away his status as a theta slave.
--->'''O'Brien''': This man [Bashir] is a doctor where he comes from. And there's an O'Brien there just like me, except he's some kind of high up Chief of Operations. They're Terrans. Can you believe that? Maybe it's a fairy tale he made up, but it made me start thinking how each of us might have turned out if history had been just a little different. I wanted him to take me with him because whatever it's like where he's from, it's got to be better than this. There's got to be something better than this.
* SpacePirates: Mirror Sisko and his crew raid ships that pass in the vicinity of Terok Nor and collect "duties" for Intendant Kira.
* TheStarscream: Mirror Garak plots with Kira to overthrow Intendant Kira. When she tries to use the information to bargain with Mirror Sisko, he laughs that Garak has been trying to kill her since the day he was assigned to the station.
* StepfordSmiler: When Intendent Kira gives Sisko a booty call, he makes a vaguely forlorn expression. By the time he turns to his men, however, he's smiling lasciviously. It seems he doesn't savor being Kira's plaything as much as he lets on.
* SupermodelStrut: Intendant Kira's default mode of walking is a sultry strut, which makes her body language stand out in contrast to Kira.
* ThenLetMeBeEvil: At first, Intendant Kira tries to justify her ruthless reign as being a show of kindness. After Mirror Odo is killed, however, she drops all pretenses.
--> "This is my reward...for treating you Terrans with the ''[[PunctuatedForEmphasis LEAST! Bit! Of respect!]]'' Very well! I can learn from my mistakes! You want to set an example, Garak? Use [Bashir], set an example for all Terrans! Slowly, in public view on the Promenade! Let his pleas for mercy ECHO THROUGH THE CORRIDORS for all Terrans to hear!"
* WeHardlyKnewYe: Mirror Quark only appears in two scenes, and Mirror Odo in just five, before they get killed off.
* WeWillUseManualLaborInTheFuture: The Alliance relies on Terran slave labor to mine ore at Terok Nor.
* WhatHappenedToTheMouse: Noted by Bashir and Kira. They meet alternate versions of Odo, Kira, Garak, Quark and Sisko, but there's no sign of Jadzia or Mirror Bashir. They do reappear in the next Mirror Universe episode.
* WhyWeCantHaveNiceThings: Intendant Kira has standing orders to execute any visitors from the main universe immediately, but she can't resist the allure of her doppleganger. Kira and Bashir only stay for a few hours, but their visit has massive ramifications throughout the Mirror Universe -- that execution order was pretty prudent.
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