Odo, Sisko, Dax and Garak find themselves warped 7 years in the past and on Terok Nor. And Odo has to find a way out of the situation without revealing a dark secret about his past.
- 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.
- 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.
- Foreshadowing: Odo being the cause of everyone's comas is the first hint that being turned into a solid is not as permanent as it seems.
- Fridge Logic: In-universe. Garak eventually realizes that the timeframe for the events is wrong; the security chief at the time of the incident wasn't Thrax, but Odo. This is one of several hints that lead to the truth being revealed at the end.
- Heroic B.S.O.D.: 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.
- 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.
- Not So Different: Much like Kira, Odo has a dark secret from his time on Terok Nor. The episode even ends with them in opposite places from the end of "Necessary Evil".
- 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.
- These Hands Have Killed: Complete with hallucinated blood on Odo's hands.
- 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.