Odo, Sisko, Dax and Garak are on a runabout heading back from a conference on the Cardassian occupation of Bajor. Garak is annoyed that his "dispassionate" view of the occupation was not received well by the Bajorans. Odo, on the other hand, was received as a hero in spite of working for the Cardassians because of his reputation for fairness, though the constable is uncomfortable with the praise. When the runabout arrives at Deep Space Nine, however, all four occupants have gone comatose. We then cut to the four occupants awakening on the promenade of Terok Nor during the Cardassian occupation.
The four apparent time travelers realize that they are a few years in the past. Gul Dukat is still the commander of the station, and the current chief of security is a Cardassian named Thrax, Odo's predecessor. They discover that everyone perceives them as Bajorans even though they see each other as their real selves. Odo is also spooked by the apparation of a walking dead man, though he reveals nothing to the others. Cardassians interrupt them and haul away Dax, saying she's been "selected" by Dukat. When Garak tries to bribe the guards, they punch him in the nose.
Meanwhile, on Deep Space Nine, the four comatose men are examined by Bashir, who notes that their brains are active. He wonders if traveling through a plasma storm has affected them somehow and resolves to do some research. When Garak is punched on Terok Nor, his body on Deep Space Nine gets a nosebleed, which Bashir thinks might be a psychosomatic response. If any of his patients believe they've been injured severely enough, they could potentially stop their own hearts.
Back on Terok Nor, the bloodied Garak reveals that he pinched a scanner from the guards and uses it to discover their Bajoran identities. Odo is familiar with the Bajorans, but before he can explain why, he's interrupted by Quark, who conscripts them to clean his bar. While they work, Odo reveals that their Bajoran identities were falsely accused of trying to assassinate Guk Dukat and executed. Meanwhile, Dax is brought before Dukat, who explains that he's chosen her to be his special Bajoran friend to talk to when he gets lonely.
Overhearing a conversation between Thrax and Quark, Garak realizes that they are seven years in the past, when Odo was already chief of security, not Thrax. Putting this mystery aside, the four meet with a Bajoran resistance member hoping to get a ticket off the station, but suddenly an explosion rocks the promenade close to where Dukat and Dax were standing. The four time travelers are quickly arrested and accused of committing the assassination attempt. Thrax visits their holding cell, and Odo pleads with him to make various investigations that would prove their innocence, but Thrax rebuffs him. Sisko is becoming increasingly aware that Odo knows more than he lets on, but he avoids elaborating and says nothing of his ghostly visions.
Dax recovers from her injuries in Dukat's chambers, but as soon as he turns his back, she knocks him out and helps the three prisoners escape. Running for the airlocks, they encounter Thrax and another guard and get into a brawl. During the fight, Thrax transforms into a changeling and escapes. With no time to ponder what that means, they keep running but suddenly find themselves right back in their cell with no explanation.
Odo requests an audience with Thrax and again pleads with him to do his job, but Thrax states that he's only interested in keeping order. He then admits to knowing who Odo is and addresses him by name. Reality becomes even more fluid as the four prisoners find themselves on the promenade ready for execution. Odo disarms the executioner, declaring that this is all his fault. Across the promenade, he sees a vision of himself wearing a Cardassian uniform and presiding over the executions of their Bajoran counterparts. He finally admits that he was the real constable during these events and failed to properly investigate the suspects' innocence before it was too late. Upon this revelation, all four patients awaken on the station.
Later, Bashir explains that Odo must have instinctively brought the other three crewmembers into a version of the Great Link. Odo is apparently still more changeling than he realized. After Bashir leaves, Kira arrives, having read the report and discovered Odo's shame. She admits that she'd placed Odo on a pedestal and has been unpleasantly surprised to discover that he's just as flawed as anyone else. She asks him if those were the only innocent people he'd allowed to die on his watch, but Odo can only state that he hopes so.
- As You Know: Sisko reminds Odo, Dax, and Garak that DS9 was called "Terok Nor" during the occupation.
- Be All My Sins Remembered: Take this trope, Sympathetic Murder Backstory, and Psychic Link, put them in a blender and you'll get the whole setup for this episode.
- Blatant Lies:
- The Cardassian guards claim Sisko, Odo and Garak had attacked Dukat, and that Sisko himself was trying to strangle the man (Sisko was standing over Dax, making sure she was alright). Odo shouts at Thrax that their stories could easily be disproved by talking to actual witnesses.
- Defied. Garak says that there's no time for him to give the perfectly reasonable explanation for why a "simple tailor" is a skilled pickpocket.
- Borrowed Catchphrase: Thrax uses Odo's own "it's been my observation" during their argument. Another bit of Foreshadowing that he's really Odo himself.
- Broken Pedestal: Kira is disappointed to discover that Odo isn't the perfect champion of justice she thought he was.
- Continuity Nod: Dukat's fondness for Bajoran woman comes up again. Dax gets chosen as his newest "friend".
- Did Not Think This Through: Garak attends a conference on the Occupation hoping to offer an "alternative view" to the Bajorans present, thinking they'd be delighted for the experience. As Dax notes, the idea of a Former Cardassian Oppressor trying to do that to Bajorans was not Garak's smartest idea.
- Dream Sequence: The vision of the past is a shared dream between the four. This is revealed relatively early in the story; the four are unconscious and the other crew members (especially Dr. Bashir) are watching over them.
- The Ending Changes Everything: All of Thrax's dialogue takes on a new light when it's revealed that it's actually Odo.
- Enemy Without: The investigator in charge, Thrax, is actually Odo when he was still working for the Cardassians, modeled after Odo's predecessor and looking like a Cardassian until Odo admits the truth. He even has an argument with himself.
- Fantastic Slur: The Resistance recruiter refers to Cardies as "spoonheads". Garak bristles at this.
- When Quark is talking to "Thrax" about not being able to sell maraji crystals, he talks about how Cardassians dislike them as if he weren't talking to one. Meanwhile Sisko observes that apparently Odo wasn't the only one who kept an eye on Quark so as to curtail his illegal dealings as much as possible; after The Reveal, this commentary is even more on-point since it turns out Odo really was the only one on the station to treat Quark this way.
- Much, to the reveal, in case Odo's behaviour and foreknowledge of what's happened weren't a giveaway, or the sheer anger he directs at Thrax.
- Gilded Cage: This is what Dukat offers Dax, giving her special privileges while also becoming his captive.
- Heroic BSoD: Odo has one as soon as he realizes exactly where he is, and it doesn't let up until a while after he wakes up.
- Innocently Insensitive: Garak tries to bring up all the good things about the Cardassians' 50 years of brutal occupation and is completely blindsided by the fact that the Bajorans take it rather personally.
- Lonely at the Top: Dukat claims this to "Leeta" when establishing a relationship with her.
- Mean Boss: Quark, for Bajorans during the Occupation. Long hours, miserable work, and two five minute breaks a day.
- My Greatest Failure: Odo let three innocent people take the fall for an attempted assassination on Dukat. His thinking about it at just the wrong time leads to the episode.
- O.O.C. Is Serious Business: Odo's twitchy behaviour throughout the episode, once he figures out who everyone supposedly is.
- Out, Damned Spot!: Odo hallucinates that his hands are covered in blood as a manifestation of his guilt.
- Railroading: Every attempt to avert the fate of the three Bajoran innocents ends up either moving the story forward earlier than expected, or completely nullifying the attempt. Odo eventually manages to save his crewmates from the fate the prisoners suffered, but the execution of the prisoners isn't averted, and everyone in the dream sees it happen—with two Odos, theirs and the one from that time, watching.
- Right Under Their Noses: Sisko uses a trick that Kira told him about to signal a meeting with the Bajoran resistance, by picking up a piece of pottery, examining it, and turning it over.
- Sex Slave: It's never stated outright, but it's clear that Dukat expects Dax to provide "companionship" in more ways than just conversation.
- The Snack Is More Interesting: Quark snidely offers slave wages to Sisko, Garak and Odo while munching on a snack.
- Tap on the Head: Dax knocks Dukat out cold with one blow to the head.
- Theory Tunnelvision: Odo only realised afterwards the holes in the case because he was so focused on maintaining order.
- Took a Level in Jerkass: A retroactive example. Quark is revealed to have been nastier when he had scores of Bajoran laborers to exploit.
- Wham Shot: Thrax suddenly revealing he's a Changeling.
- Your Mind Makes It Real: An injury suffered by one of the four unconscious crew members manifests itself in reality as a burst blood vessel. Bashir speculates that a death in the dream state might result in a death in reality. On the other hand, he also discusses realistic limitations of it, citing they probably can't spontaneously break their own bones.