The first installment of the show's nine-episode finale follows three plotlines. In the first, Kira announces that Worf's ship has been destroyed in the badlands, and he is presumed lost. The mournful Ezri breaks into Worf's quarters and relives her time with him as Jadzia. Moved to action, she steals a runabout and flies to the Badlands to search for Worf. Sisko calls her back but decides not to chase after her. She manages to retrace the steps of Worf's escape pod and locate him. After beaming him aboard, however, the two quickly proceed to bickering, still uncomfortable with their situation. The fight is cut short when they're attacked by Jem'Hadar and forced to beam to a nearby planet. Stranded without any communicators, the pair start quarreling again before the fight turns romantic. However, their postcoital bliss is prematurely ended by Breen, who abduct them to their ship headed for who-knows-where.
On Cardassia, Damar and Weyoun are busy with a new communications relay. Damar is grating under the Dominion's leadership, particularly from how costly the war has proven in Cardassian lives, but Weyoun will hear no disobedience. He goes to the Female Changeling to report their progress but has no good news about a vaccine to cure her degenerative disease. She orders all of the Vorta scientists to record their findings and be executed and replaced by their next clones to get a fresh perspective on the problem. Meanwhile, Dukat meets with Damar, still proselytizing about the pah-wraiths, and asks a favor. Damar obliges and gives Dukat the use of surgeons who make him appear Bajoran as part of some unspoken plan.
Back on the station, Sisko begins planning out his retirement home on Bajor, selecting the land and starting to model out his house. As he discusses his plans with Kasidy, he tells her that he wants it to be her home as well, and he promptly proposes. She accepts, and they begin planning a simple wedding. However, it soon becomes clear that the Bajorans have found out about the Emissary's impending nuptials and expect a grand, state wedding. Before that can happen, Sisko gets a vision from the Prophets in the form of his mother, who tells him that he must not get married and instead walk alone so that everything will be as it should be.
Tropes in this episode:
- Abandon Ship:
- Worf and Ezri are forced to beam off the runabout just before it explodes.
- Worf is lost at the beginning of the episode after abandoning the Koraga.
- Bad Boss: The female changeling tells Weyoun to execute the Vorta doctors and activate their clones, thinking it might give them a fresh perspective.
- Book Ends: One for the Final Chapter. The Dominion War kicked off with a multi-episode arc and the climax of the War likewise kicks off with a multi-episode arc.
- Call-Back: In "Favor the Bold," Sisko told Ross that he wanted to build a house on Bajor. Now he's putting his plans into motion.
- Continuity Nod:
- Weyoun orders Damar to redirect ships to protect a Son'a outpost. In Star Trek: Insurrection, it was mentioned that the Son'a were supplying the Dominion with ketracel-white. Since the Final Chapter takes place after the events of the film, the implication is that despite Picard's best efforts, at least some of the Son'a haven't reconciled with the Ba'ku in the wake of Ru'afo's death.
- Another reference to Captain Boday and his transparent skull, as well as Jadzia's fling with him.
- Continuity Overlap: As with the preceding episode, enough time had passed since the release of Insurrection to finally sync up DS9 with the events of the film. The mention of the Son'a Outposts is the closest the series gets to acknowledging what happened in the Briar Patch.
- Even Evil Has Standards: Loyal he may be to his gods, but even Weyoun's a little taken aback at the Female Founder so casually ordering the immediate execution of Vorta doctors.
- Fake Static: Ezri's attempt isn't convincing at all.Sisko: Cut it out, Old Man. I'm not buying it.
- Foreshadowing: Next episode we find out who the changeling is talking to over subspace.
- Going Down with the Ship: Worf is the last one off the Koraga.
- No One Gets Left Behind: Discussed between Damar and Weyoun re the search for survivors from the Koraga. It gives Damar the chance to vent his frustrations over the losses that Cardassia has suffered.
- Pardon My Klingon: When Worf finds out that Jadzia had slept with Captain Boday, he angrily calls Ezri a sli'vak, which seems to be the Klingon word for "whore."
- Pet the Dog: Quark comforts Ezri and advises her to not give up hope on Worf even though the Klingon is his rival for Ezri's affections.
- Redemption Rejection: Implied to be the case with the Son'a, or at least the faction of Son'a who're still working with the Dominion in spite of the events of Star Trek: Insurrection.
- Slap-Slap-Kiss: In the midst of a fight, Ezri slaps at Worf, who catches her hand, and they commence snogging.
- Slut-Shaming: Worf is quite cross to find that Jadzia had relations with Captain Boday (and possibly others aboard DS9) before they had met.
- Sure, Let's Go with That: Weyoun figures that Damar's agitation has to do with a lady friend waiting for him. Damar plays along, not telling him that he's working with Dukat.
- Survival Mantra: "I am not spacesick. I am not spacesick..."
- Symbolism: The episode title. A penumbra is the outer, lighter area of shadow formed when a celestial body is partially eclipsing another (i.e., by the moon when it passes before the sun, or the earth when it does). The implication is that the war with the Dominion is moving into its final, most dangerous act and the heroes will be facing their Darkest Hour (or as the Prophet-vision of Sisko's mother tells him, a "great trial" is imminent). note It also applies metaphorically to Kai Winn's descent into the evil of the Pah-wraiths over the next two episodes.
- This Is What the Building Will Look Like: Sisko starts building a scale model of his future house on Bajor.
- Ungrateful Bastard: Ezri chews Worf out for not showing more gratitude to her for rescuing him.
- Wham Shot: Dukat as a Bajoran.
- Why Did It Have to Be Snakes?: Ezri, who suffers from spacesickness at the best of times, ends up having to ride a plasma current in the Badlands to find Worf. She clearly has trouble dealing with the turbulence.
- Will They or Won't They?: Ezri and Worf? They will.
