The crew on the station braces for battle against the newly arrived Dominion fleet, only for it to fly past them and into Cardassian space. [[Characters/StarTrekDeepSpaceNineGulDukat Gul Dukat]] follows them and announces that the Cardassian Union has joined the Dominion under his leadership. In the internment camp, the Cardassian prisoners are released, all except Garak, who is forced to stay by Dukat's orders.

The prison gang hatches a plan to contact their runabout and make their escape. Only Garak knows enough about engineering to do it, so it's up to him to rummage around inside the walls and jury-rig machinery while the rest provide a lookout. Worf is selected as fresh meat for the Jem'Hadar's daily gladiatorial fights and holds his own in an ongoing series of battles, though he emerges more injured after each day.

On the station, a fleet of Klingon ships led by Chancellor Gowron himself arrives, having just given battle to the Dominion. Sisko convinces the chancellor to renew the Khitomer Accords so that the Federation and the Klingon Empire can make a joint stand at the station. Meanwhile the Changeling masquerading as Bashir suggests initiating blood screenings to ferret out Changelings, apparently confident of his ability to pass as human.

In the camp, Garak is grappling with his suppressed claustrophobia. After getting locked in the crawlspace in the dark, he finally has a meltdown and goes a bit catatonic. The others lament that he's their only hope of escape. Further, while Worf has won the gladiator games time and again, he's barely holding himself together. But then Garak snaps back to his chipper old self and returns to the crawlspace to continue his work. Even Worf and Martok are impressed by the Cardassian's courage.

On the station, Romulan ships arrive without warning and announce that they want to join the fight. Sisko launches the ''Defiant'' and all of his runabouts for the impending battle, but the Changeling has infiltrated the ''Yukon'' and incapacitated its crew. He flies directly toward the Bajoran sun in a ship packed with high-tech explosives. The station starts picking up phantom signals of the Dominion fleet all around them, like they've been surrounded by a cloaked armada.

Things are just as dire on the camp. The injured Worf faces the Jem'Hadar's First in the ring. It's not a fair fight, and he starts getting pummeled. Meanwhile, the Jem'Hadar are looking for Garak and discover his crawlspace. They start shooting members of the escape cell, demanding that Bashir fess up to what's going on. Suddenly, the Breen in their company grabs a disruptor and starts blasting. It's a shootout, and when the dust settles, our heroes have survived and all the guards are disintegrated. By this point, Worf is barely clinging to life but refuses to surrender. The First yields in his place, announcing that he cannot defeat Worf, only kill him. Disgusted, the resident Vorta orders both killed, but Worf is transported away just before he can be gunned down. Our heroes have escaped!

Bashir sends a message to the station, and Sisko quickly deduces that his double is an imposter. He tracks the double's last location to the ''Yukon'' and orders it destroyed. The runabout is on a collision course with the Bajoran sun with the intent to make it go supernova, destroying the entire solar system and all the ships stationed there. Kira orders Dax to use the ''Defiant'''s warp drive to catch up to in a desperate move, and it works. The runabout is destroyed harmlessly, and all traces of the phantom Dominion fleet vanish. The whole threat of attack was part of the Dominion's ruse.

The escapees return to the station. Garak and Worf have happy reunions with Ziyal and Dax. O'Brien grapples with the fact that he's been palling around with a Changeling for a month without realizing it. The Klingons will now have a permanent presence on the station, with Martok as their commander. Dukat messages Sisko to congratulate him on averting destruction. The captain notes that his actions saved Ziyal's life, but Dukat says that he's disowned her. They exchange threats before ending the conversation.
----
!!Tropes
* ActorAllusion: A possible one: actor Creator/AlexanderSiddig, who plays Dr. Bashir (and his changeling doppelganger), is the real-life nephew of actor Creator/MalcolmMcDowell, who had played [[BigBad Dr. Tolian Soran]] in ''Film/StarTrekGenerations''. Here, the changeling Bashir tries to blow up a star using a Trilithium explosive, just like Soran did in the movie.
* ApocalypseHow: Attempted by the changelings on a [[ApocalypseHow/ClassX2 stellar]] scope; {{Defied}} by Major Kira.
* BadassBoast:
-->'''Ikat'ika:''' Prepare yourself! I found your WorthyOpponent.\\
'''Worf:''' Where is he?\\
'''Ikat'ika:''' [[PreAssKickingOneLiner Right in front of you.]] Victory is life.\\
'''Worf:''' Today ''is'' a good day to die.
* BatmanGambit: The Dominion anticipated that the Federation and Klingons would make a stand at the station, which is why they plotted to destroy Bajor's star. The resulting shockwave would cripple both fleets, as well as destroy the station and leave the wormhole up for grabs.
* BewareTheQuietOnes: The Breen prisoner does nothing but sit silently on a bunk in the cell for the whole episode until the guards decide to investigate the secret panel behind which Garak is working on an escape mechanism.
-->'''Romulan:''' My people have a saying: "Never turn your back on a Breen."
* BrickJoke: Jadzia kept Worf's opera collection intact...more or less.
* BringIt: Dukat informs Sisko that if he doesn't surrender the station, he will take it by force. Sisko replies that he's welcome to try.
* CallBack: When the Jem'Hadar release their Cardassian prisoners and announce that Cardassia has joined the Dominion, Garak assumes he'll also be freed. He's proven wrong when the Jem'Hadar mention that they were told to specifically ''not'' free Garak. [[Recap/StarTrekDeepSpaceNineS03E07CivilDefense Looks like Dukat remembered to make an exception for Garak this time]], just like he said he would.
* ConflictKiller: The arrival of the Dominion convinces Gowron to end the Klingon-Federation conflict, re-sign the Khitomer Accords, and throw the Empire's lot in with the Federation to stand against the Dominion.
* ContinuityNod: The changeling's attempt to blow up a star with a Trilithium explosive is a nod back to ''Film/StarTrekGenerations''.
* CurbStompBattle: Worf loses very badly against Ikat'ika. Having been through seven fights already, none of which were easy wins, he's too injured to offer any resistance beyond refusing to submit.
* DayOfTheJackboot: After a year and a half of democratic rule, Cardassia is once again ruled by the fascists, in this case Dukat and the Dominion.
* DemocracyIsFlawed: The Cardassian people had been living under a fascist government for a long time before Central Command was overthrown, and the civilian government had been wracked by one crisis after another. It's no surprise a democratic government wouldn't survive long in such a political environment.
* {{Determinator}}:
** Worf absolutely ''refuses'' to give up the fight against the Ikat'ika, even though he can barely stand up. His valor winds up earning him the Jem'Hadar First's respect.
** Garak does his best to press on with his work in the cramped space in spite of his {{claustrophobia}}, until he suffers a crippling panic attack when his [[TentativeLight jury-rigged light]] goes out. Once he's recovered enough, [[FaceYourFears he goes right back to work]]. Even Worf and Martok are impressed at his fortitude.
* DidntSeeThatComing: A fleet of Romulan ships de-cloak around the station and requests permission to join the fleet.
-->'''Sisko:''' I'll be damned. Permission granted.
* DudeWheresMyRespect: Dukat demands that Sisko show him more respect as the head of the Cardassian government. Sisko tells him to stuff it.
* EasilyForgiven:
** Despite just having been at war with them, the Federation quickly re-allies with the Klingons without pause. They both already know that they were manipulated into war by the Dominion, and they now have a chance to fight their mutual enemy together. It also helps that [[Recap/StarTrekDeepSpaceNineS05E01ApocalypseRising not that long ago,]] while Gowron couldn't push for a ceasefire with the High Council between the Empire and the Federation with Klingon bloodlust ignited, now they have a mutual enemy to turn that passion for war against.
** Also the case for the Cardassians and the Dominion. Despite the Female Changeling making it clear the Founders held ''all'' Cardassians responsible for trying to genocide them, they are perfectly happy to let Cardassia join the Dominion, mostly because it [[JustifiedTrope furthers their own agenda]] by [[PragmaticVillainy giving them a foothold in the Alpha Quadrant]].
* EnemyMine:
** The Klingons ''and'' Romulans put their problems with the Federation aside to join against the Cardassian-Dominion threat. The Klingons even re-sign the old Khitomer Accords.
** Not to mention all the prisoners in the compound to escape. ''Especially'' the Romulans and the Breen.
** The Dominion ally with their enemies, the Cardassians, against their common foes: the rest of the Alpha Quadrant.
* EvilCannotComprehendGood: Deyos can't understand Worf's refusal to stay down in a fight he can't win. Ikat'ika (another villain, ironically) understands perfectly, and coldly criticizes the Vorta for his lack of honor.
* EvilerThanThou: The Dominion proves this to the Klingons, forcing Gowron into an EnemyMine with the Federation.
* EvilIsPetty: Because the Cardassians are now allies with the Dominion, all the Cardassian prisoners in the prison are freed. However, Dukat ''explicitly'' forbids Garak from being one of them.
* EyeScream: Martok attributes his missing eye to Ikat'ika.
* FaceHeelTurn: While never much of a Face to start with, Dukat was nevertheless a semi-reliable ally to the crew of [=DS9=] during season 4. Here, he sells his people to the Dominion and reestablishes himself as one of the show's main antagonists.
* FaceYourFears: Garak faces his severe claustrophobia to finish his work on the transmitter. Even Worf and Martok are impressed.
-->'''Martok:''' There is no greater enemy than one's own fears.
-->'''Worf:''' It takes a brave man to face them.
* FamedInStory: Martok promises that Worf will have a song written about his fight against the Jem'Hadar. He also offers to include Bashir, "the healer who bound the warrior's wounds so he could fight again!" Garak then [[DeadpanSnarker points out]] that the Cardassian who panicked in the face of danger would ruin Martok's heroic epic, and resolves to finish the job he started [[FaceYourFears in spite of his claustrophobia]].
* FinishHim: Deyos orders Ikat'ika to kill Worf after kicking his ass. Ikat'ika, however, concedes the fight, as he failed to break Worf's spirit.
* FireForgedFriends:
** While "friends" is likely too strong a word, Worf and Garak have a new esteem for one another after their experiences in this episode.
** Worf's hardiness earns Martok's respect, beginning a bond between them that will last for the rest of the series.
* GodzillaThreshold: Travelling at warp within a solar system is portrayed as a dangerous maneuver, but Kira points out that if they don't, there won't be a solar system ''left''. It's worth noting that they're warping directly toward ''a star'', so a slight miscalculation would equal one crispy ''Defiant'' (and probably wouldn't be very good for the star either).
* GondorCallsForAid: Sisko convinces Gowron to rejoin the Khitomer Accords, allowing the Klingons to join Starfleet for the defense of the wormhole. Surprisingly, an entire Romulan fleet also joins in to help their foremost enemies.
* TheGuardsMustBeCrazy: The Dominion did a pretty good job creating an inescapable asteroid prison, but for some unexplained reason they left Worf and Garak's runabout in orbit, fully operational and unguarded. And also had no type of surveillance in the cells...
* HeroicRROD: Worf repeatedly fights and wins against Jem'Hadar, but gets hurt in each fight and his injuries pile up very quickly. Bashir states after five fights he's got multiple broken ribs. By the time he faces Ikat'ika, Worf is too injured to offer real resistance and fails to land a single blow.
* HiredToHuntYourself: Sisko assigns Dr. Bashir to start blood-screening the crew of Deep Space 9 to identify the Changeling infiltrator who sabotaged the deflector array, not knowing Bashir ''is'' the Changeling they're looking for. The spy was the one who suggested it, so he must have been pretty certain of his ability to avoid detection. Based on past instances where Changelings managed to get around it (most notably the Martok Changeling when he first appeared in "The Way of the Warrior"), and Sisko's dad's commentary on the subject back in the "Homefront" / "Paradise Lost" two-parter, it seems he was right to be.
* HonorBeforeReason:
** Why Worf continues to fight a losing battle, even after Ikat'ika (his opponent) and Martok (another Klingon) tell him to give up.
---> '''Martok:''' Worf, honor has been satisfied. Stay down.
** Also discussed before the fight begins:
--->'''Deyos:''' You fight because that is what you were designed to do. All that motivates him is some barbaric sense of honor.\\
'''Ikat'ika:''' And that is something you will never understand.
* HopeSpot: The Vorta announces that Cardassia has joined the Dominion and so all Cardassian prisoners are going home. Garak gives a nod to Bashir, indicating that he'll use his freedom to get help, but then it turns out that Dukat intervened personally to ensure Garak would not be released.
* HumbleHero: Worf, as far as Martok is concerned.
--> '''Martok:''' ''Seven'' matches, and ''seven'' victories! What hero of legend could have done as well?\\
'''Worf:''' ''(limping)'' Heroes of legend do not ache so much.\\
'''Martok:''' Your Federation friends have taught you modesty.
* ILikeThoseOdds: A variation at the beginning, as the ''Defiant'' faces down a Jem'Hadar fleet along with two runabouts and (they think) Dukat's Bird-of-Prey.
-->'''Dax''': There sure are a lot of them.\\
'''Kira''': That'll just make it harder for us to miss.
* IOweYouMyLife: Dukat freely admits that Sisko saved his life at least once, and returns the favor by giving him a chance to surrender the station peacefully. Sisko, clearly regretting not just letting Dukat die, tells him where he can stick it.
* IWillPunishYourFriendForYourFailure: The Jem'Hadar try to use this against the inmates, threatening to kill some of them unless someone gives up the truth. They only actually kill one person before the prisoners manage to fight back.
* LeaningOnTheFourthWall: Dukat asks Kira to admit that being on the same side "never really felt right." This sounds a lot like the writers admitting their own problems with Dukat's arc.
* MutualKill: The Breen prisoner and a Jem'Hadar guard vaporize each other.
* NeckSnap: How Worf kills one of his Jem'Hadar opponents.
* NewEraSpeech: Dukat delivers one after he removes the Cardassian civilian government from power.
-->"You might ask, should we fear joining the Dominion? And I answer you, not in the least. We should embrace the opportunity. The Dominion recognizes us for what we are: the true leaders of the Alpha Quadrant. And now that we are joined together, equal partners in all endeavours, the only people with anything to fear will be our enemies. My oldest son's birthday is in five days. To him and to Cardassians everywhere, I make the following pledge. By the time his birthday dawns, there will not be [[CurbStompBattle a single Klingon alive inside Cardassian territory]] or [[FinalSolution a single Maquis colony left within our borders]]. Cardassia will be made whole. All that we have lost will be ours again, and anyone who stands in our way will be destroyed. This I vow with my life's blood. For my son, for all our sons."
* NobleDemon: Ikat'ika coldly criticizes Deyos (his boss) for lacking any understanding of honor, and is ultimately so impressed with Worf that ''he'' surrenders, admitting that he can only kill Worf, not defeat him. This principled stand gets Ikat'ika shot.
* NoGoodDeedGoesUnpunished: If the [=DS9=] had just destroyed the wormhole with some torpedoes, then the threat of the Dominion invading within the lifetimes of the crew would have been all but ended, albeit at the cost of stranding Worf and Garak in the Gamma Quadrant, and probably ending any chance of the Bajorans ever joining the Federation. Instead, their going with the plan to seal it without harming the Prophets allows the Bashir Changeling to sabotage it, causing them to instead end up making the wormhole totally indestructible.
* NoodleIncident: While working inside the wall, Garak mentions an incident where he was trapped in some kind of small space on the Tzenkethi homeworld, apparently involving a lack of air and walls threatening to collapse.
* NotSoWellIntentionedExtremist: In his NewEraSpeech, Dukat makes a good show of his brokered alliance with the Dominion being a patriotic move to save Cardassia from the threats of the Klingons and the Maquis. A more private chat with Sisko implies a less noble, more self-important motive.
-->'''Dukat:''' You should see the monument they're erecting in my honor at the gateway to the Imperial Plaza.\\
'''Sisko''': Is that why you sold your people to the Dominion? For a ''monument''?
* NothingIsTheSameAnymore: The Dominion now has a foothold in the Alpha Quadrant in the form of Cardassia, Dukat threw his lot in with the Dominion, and war is appearing just over the horizon.
* OhCrap:
** The look on Garak's face when he finds out who's running Cardassia:
---> '''Deyos:''' ''Gul Dukat''.
** The Bashir changeling has this look when his runabout gets tractor-beamed short of his target.
* RageBreakingPoint:
** Dukat takes a moment as the Dominion fleet suddenly shifts towards Cardassia to gloat to Kira that he has negotiated for Cardassia to join the Dominion, before adding as a parting shot that the two of them on the same side "never seemed quite right, did it?" Kira's response (after a minute ago making it clear they were on "hold fire" orders until Sisko gave the word):
--->"Lock phasers, open fire!"
** Then, later after hearing the aforementioned NewEraSpeech she had this [[TranquilFury to say in response]]:
--->"Well, I've got a vow to make too. The next time I see Dukat, I'm going to kill him."
* RedHerring: It was established in the previous episode that Bashir couldn't test the Breen prisoner via blood screenings, because [[BizarreAlienBiology the Breen had no blood to test]]. This set up suspicion that the Breen might have been a Founder spy. Nope; the Breen actually ''was'' a prisoner... and proved it by sneak-attacking a Jem'Hadar guard, [[MutualKill before the Breen and a second guard killed each other]].
* SadisticChoice: Dukat tells Sisko to either surrender the station or he'll retake it. Sisko basically tells him to BringIt.
* SeeTheWhitesOfTheirEyes: Used and averted. Used in that the ''Defiant'' has to get very close to the ''Yukon'' in order to use the tractor beam on it. Averted in that they were shooting the ''Yukon'' from far enough away that they had to make a brief jump to warp to get close enough to tractor beam it.
* SensorSuspense: With what looks like a fleet of Dominion ships. Turns out to be a distraction while the changelings carry out their real plan.
* SmallRoleBigImpact: The unnamed Breen prisoner manages to steal a weapon from a Jem'Hadar guard and kills two of the guards whilst dying in the process. Without the Breen's actions the other prisoners would've probably died, which means they never would've warned the [=DS9=] crew about the fake Bashir, which in turn means his plan would've worked, so Bajor, the allied fleet and Deep Space Nine would've been annihilated and the Dominion would've dealt a devastating first strike in the war against the Alpha Quadrant powers.
* TheSpeechless: The Breen prisoner hangs around the plotting prisoners, rescues everyone and gets vaporized all without ever saying a word.
* SpotTheImposter: Discussed at the end of the episode, where O'Brien is stunned to learn he spent over a month associating with a Changeling.
-->'''O'Brien:''' And the worst part is, the clues were right in front of me.\\
'''Bashir:''' What clues?\\
'''O'Brien:''' Well, for one thing, he was a lot easier to get along with.
* ShoutOut: General Marok telling Worf to stay down after taking a beating from Ikat'ika is almost identical to Luke being told by the other prisoners to stay down after taking a beating from Dragline in ''Film/CoolHandLuke''.
* StarKilling: The Dominion tries to destroy Bajor's sun with a protomatter/trilithium device.
* StatusQuoIsGod: [[Recap/StarTrekDeepSpaceNineS04E01E02TheWayOfTheWarrior A year and a half after its sundering]], the Khitomer Accords are reinstated and the Federation-Klingon Alliance that's been a foundation of the ''Next Generation'' era is officially back in business.
* SuicideAttack: The Bashir changeling attempts one against the entire Bajoran star system (he clearly had no way of escaping, or he'd have used it). The ''Defiant'' pulls his runabout away at the last second, though, resulting in a look of horror as he realizes he's dying for nothing.
* TakingYouWithMe: The Breen prisoner kills a Jem'Hadar guard in a sneak attack, then the prisoner and a second guard kill each other.
-->'''Female Romulan:''' My people have a saying: "Never turn your back on a Breen."
* TalkingToTheDead: Garak tells the recently-deceased Tain that he could use his help.
-->'''Garak:''' Tain, I don't know if you can hear me, but if you can I just want you to know you may not have been much of a father, but I really wish you were alive right now. That way you could be in here instead of me.
* TentativeLight: At one point, Garak's light source becomes temperamental, which threatens to trigger his claustrophobia. When the light goes out, a panic attack ensues.
* ThinkingOutLoud: Garak trying to stave off his claustrophobic breakdown. It doesn't work.
-->'''Garak:''' ''(to the [[TentativeLight flickering light source]])'' I'm sorry, but that's absolutely unacceptable. I'm under enough strain as it is, I can't have you quitting on me. Get a hold of yourself, Garak. After all, you haven't had one of these attacks in years. Yes, this is a tight enclosed space. Yes, there's not a lot of room to move. But a disciplined mind does not allow itself to be sidetracked by niggling psychological disorders like claustrophobia. Besides, this isn't like Tzenketh. The walls won't collapse in on you. Your friends are near by, there's plenty of air, so there's nothing to be concerned about. Focus on the job. You're the only person who can contact the runabout. People are depending on you. Ziyal is depending on you. You promised her you'd come back, and that young lady has had quite enough disappointments in her life without you adding to them, so control yourself. You're stronger than this. A disciplined mind-- ''(the light goes out, and Garak starts panicking)''
* VictoriousRoar: Worf roars in victory after dispatching one of the Jem'Hadar.
* VoiceChangeling: The Changeling impersonating Bashir is able to imitate a female voice.
* WhamEpisode: Dukat joins the Dominion, installing himself as the leader of Cardassia and giving the Founders a foothold in the Alpha Quadrant. Meanwhile, Gowron rejoins the Khitomer Accords, making the Federation and Klingons allies again.
* WhamLine:
** Courtesy of Dukat before the teaser is finished.
--->"I'm not ''attacking'' the Dominion fleet, Major. I'm ''joining'' it."
** Also when he reveals in his private talk with Sisko that his line in the NewEraSpeech that "All that we have lost will be ours again" was a case of ExactWords: "A few days ago, I swore all Cardassia lost would be regained. That space station you're so fond of was ''built'' by Cardassia."
* WhatYouAreInTheDark: A low-key example, but when Garak is having his claustrophobic panic attack, he explicitly states that his ''friends'' are nearby, acknowledging that he genuinely trusts at least Bashir and Worf despite his usual suspicious attitude.
* TheWorfEffect: Played with. [[TropeNamer Worf]] defeats several Jem'Hadar in a row (while suffering more and more injuries), but eventually he ends up facing Ikat'ika, who [[NoHoldsBarredBeatdown wipes the floor with him]]. Worf's {{Determinator}} spirit, however, remains unbroken, and in the end it's ''Ikat'ika'' who yields. Ultimately this episode was one of the most determined attempts to [[DefiedTrope defy]] and undo this trope.
* WorfHadTheFlu: By the time Worf fights the Jem'Hadar First of the prison, Worf has already experienced progressive injuries from his previous 7 opponents, which Bashir can only do so much about under the circumstances.
* WorthyOpponent: Worf kicks several different kinds of ass during his forced fights on the prison asteroid. His sheer determination earns him the respect of the Jem'Hadar in charge.
-->'''Ikat'ika''': I yield. I cannot defeat this Klingon. All I can do is kill him. And that no longer holds my interest.
* {{Unperson}}: A political variation. As Starfleet's ranking officer in the Bajoran Sector, Sisko refuses to recognize the new Cardassian 'government' (not that Dukat cares and considers his lack of recognition irrelevant).
* YouHaveFailedMe:
** The Vorta Deyos has Ikat'ika killed for yielding to an opponent he was winning the fight against. He also tries to have Worf killed at the same time, but Worf gets [[TeleportationRescue beamed out at that moment]].
** Ziyal refuses to come with Dukat and has a crush on Garak, so Dukat decides to not acknowledge her as his daughter any longer.
--->'''Dukat:''' Ziyal made her choice. As far as I'm concerned, [[IHaveNoSon she is no longer my daughter]].