Star Trek: Deep Space Nine

In the documentary What We Left Behind, former DS9 show runner gathered some of the old staff writers and came up with a theoretical idea for the first episode of an eigth season to Deep Space Nine, set 20 years after season 7 ended, to account for how much time had passed.  

The exercise was never meant to be canon, instead it was meant to give viewers a glimpse into how the writers' room worked and to be a fun reunion for them. 

The Star Trek wiki, Memory Alpha, captured how the writers' imagined first episode of season 8 would have played out. 

Teaser

Nog, now captain of the USS Defiant, evades weapons fire from a cloaked ship. The Defiant manages to escape through the Bajoran wormhole, and the crew is relieved to arrive at Deep Space 9. (A whiteboard claims they are on a Runabout as opposed to the Defiant.)

Act One

Two weeks earlier...

Deep Space 9 is now a religious shrine, with large statues of the Emissary along the Promenade. Kira is still in charge of the station, and is now a vedek. Bajor has still not joined the Federation, and there are minimal Starfleet personnel on the station.

Quark steps into Kira's office. She is inquiring about an invitation on her PADD, asking if it is true. On Earth, it is 2395. O'Brien is the dean of mechanical engineering at Starfleet Academy. He gets an invitation to return to DS9. Keiko says it will be a chance to see Molly, who is twenty-six and serving in Starfleet.

Ezri is now captain of a ship called the USS Emmett Till, in the Gamma Quadrant, "boldly going." (A whiteboard describes the ship as the "Nightengale" (sic), a medical ship.) Julian Bashir is the ship's CMO, and they are happily married. (The whiteboard adds that they have a "challenged" twelve-year-old daughter, Eddy.)

Worf is on Qo'noS. Martok is old, and Worf is going to be his successor. Martok tells Worf to go to Deep Space 9 to see what is happening there.

Jake is living in New Orleans as a successful but isolated writer. He gets an invitation from Quark, but immediately deletes it. He then goes to take a sonic shower, but is surrounded in bright white light.

Back on DS9, everyone reunites in Quark's. Quark still has everyone's bar tabs, and points out that there is interest accumulated. (Morn is still visible in the bar.) Amidst the reunion, everyone talks about Sisko's absence. There is frustration and disappointment that he has never returned. Jake is the last one to arrive at the station. It is revealed that everyone has been invited to bid farewell to Vic Fontaine, who is dying. Vic says that the real reason for the invitation is not him. Nog instructed Quark to gather everyone. He appears on a viewscreen in the holosuite, and apologizes for the false pretenses. As he is about to explain further, the Defiant explodes, killing Nog and everyone aboard.

Act Two

Major Palik of Bajor tells everyone in the briefing room that the destruction of the Defiant was an accident. Later, everyone is mourning the loss in Quark's, and they start to reason that it was not an accident. Worf says that a certain treaty is very specific when it comes to the death of Federation citizens, and that Ezri is in charge of investigating what happened.

Ezri visits Kira in her office, and explains to her and Palik that the Federation has jurisdiction. Kira gives her three days to conduct the investigation. After Ezri exits, Palik remarks that this is going to be a problem.

Later, Kira walks along the Promenade with a young Starfleet officer, flattering him, and asking that, as a special favor, she see the data from the investigation before Ezri does. She walks away, and the officer is approached by Jake. It is revealed that the science officer is Joseph Yates-Sisko. Jake says that his father came to him in a vision and told him to come home.

Act Three

O’Brien and Bashir discuss the investigation, but all they find are dead ends. The question remains, what was Nog doing in the days before his death?

Ezri and Molly interview the few Starfleet officers remaining on the station. The Federation presence on the station is small and powerless. They say that Nog had an obsession over the last few weeks. He and Kira had a major blowout the day before he left. Ezri confronts Kira over this new information. She says it was unrelated to what happened, and she will handle the investigation from here. She then says she wants Ezri off the station.

Worf, aboard a Klingon Bird-of-Prey, beams down to caves on Bajor and meets up with Garak. Knowing Worf is a man of honor, Garak has reached out to him. He warns Worf not to trust the Bajorans, especially Kira. Garak then provides proof that Vedek Kira, on a missionary excursion, has converted Jem'Hadar to be the new Bajoran army. Nog likely discovered this, which was why he was killed. Worf is told that he has no friends here, and not to trust anyone.

Elsewhere, Section 31 feels that religion, due to being divisive, has to disappear from Bajor. They plan to destroy the wormhole and, along with it, the Prophets. The Bajorans will then join the Federation, once their religion is out of the way. Julian Bashir, as an example of a character who has lost his way, is now in charge of Section 31.

Act Four

There have been tensions between the Federation and the Bajorans. Palik is specifically concerned that some element of the Bajoran government might be implicated in a crime. There is pressure being put on Kira to expel the Federation. Kira is worried about her secret of the Jem’Hadar army.

Rom is called in, and there is a "state funeral" for Nog.

Joseph meets Jake in a cargo bay and reveals that Starfleet killed Nog; Section 31 knew that he knew something and killed him. (What he really knew was their plan to kill the Prophets.)

Act Five

The crew is gathered at Quark's, lamenting that Kira is kicking them off the station, but they do not want to go. Bajoran security officers arrive and draw their weapons. There are Klingon and Bajoran ships around the station, as well as the Emmett Till. Tensions are high.

Kira arrives and Palik tells her he has his orders. She steals a guard's weapon and stands with her friends. As they are about to shoot at each other, there is a bright white light, and Benjamin Sisko reappears. Simultaneously, he also appears on the Klingon bridge, and the Bajoran bridge. Lastly, Jake is standing in the station office, examining his father's old baseball. Sisko appears to him and says, "I'm sorry, Jake. I lost track of time."

The episode ends on a cliffhanger.

While only the first episode was imagined, some thought was given to how it would fit into the eighth season as a whole. For example, when one of the writers suggested Kira could bring Odo back from his homeworld to investigate Nog's death, it was shot down under the idea that his re-appearance should be saved until later into the season.

Behr also gave an idea on the big theme that the season tackle: 

But I will say, what I would think was next for Sisko was that he would have to re-find his Humanity. Because once you've basically lived with the gods, or become a wormhole alien which is almost the equivalent of being a god, it's finding your way back to your simple Humanity that matters. People sometimes get too above the fray. I think that's happening in this country, in a weird way. In the last couple of years we thought we were above all this, and people now are realizing that they have to come down and fight for the right to have the freedoms that they were thought were theirs by birthright. And this country and its freedom and democracy could all be taken away very fast. There will always be people who want to take it away, so you have to be willing to fight for it. How much would Sisko's sons mean to him in order to reach back into his Humanity?

As for who would be the season's Big Bad? Look no further than Starfleet's own Section 31. Behr said:

Section 31 came very late in the game. As we show in What We Left Behind, if there was an eighth season, Section 31 is the direction the show was going in. After the Dominion how can you come up with another villain? The villain would have to be on the inside, and it seemed like an absolute normal progression for Deep Space Nine to see how the Federation would stand up if the villain was us. We showed restraint with Section 31 because we ran out of time.