Star Trek Deep Space Nine: Emissary

The episode begins with a flashback to the Battle of Wolf 359. Lieutenant Commander Benjamin Sisko is the first officer of the USS Saratoga, which has just engaged the Borg Cube at that battle. The ship is quickly overpowered and the crew and family members are forced to evacuate. Sisko manages to save his son, but his wife Jennifer is killed as the ship begins to collapse.
Moving forward three years, Sisko is informing his son Jake that they will be moving to a space station, called "Deep Space Nine", in orbit around the planet Bajor. The planet was under the occupation of the Cardassian Union, but has now been freed because of the retreat of Cardassian forces from the planet. They soon arrive and discover the station in ruins. He also meets his new first officer, Major Kira Nerys of Bajor. She informs him that she does not trust him and does not like the Federation.
A break-in at a supply post on the station summons Sisko, Kira, and the Chief of Security, Odo, to the scene. One of the thieves tries to kill Odo, but he reveals himself to be a shape-shifter and easily overpowers the criminal. He also arrests Nog, a young Ferengi who is the nephew of the local bartender Quark, who is planning on leaving the station within a few days.
With this incident resolved, Sisko is called to meet with Captain Jean-Luc Picard, who is present at the station aboard the USS Enterprise. The conversation is a tense one as Sisko shows Picard only perfunctory respect and makes no attempt to hide his defiant dislike for Picard. Sisko makes a point of telling Picard that when Picard, as Locutus Of Borg, led the Borg attack against the Federation at Wolf 359, Sisko lost his wife who was aboard the USS Saratoga and now has to raise his son as a single parent. Picard does not respond to Sisko's thinly veiled anger and informs Sisko that his assignment on Deep Space Nine is to ensure that Bajor can be made ready for acceptance into the Federation. Sisko says that he will do what he is ordered to, but that he will likely be leaving Starfleet soon to pursue a civilian career on Earth where he would be better placed to raise his son as a single parent. Picard dismisses Sisko, who returns to the station.
Back on the station, Sisko and Odo meet with Quark to discuss the future of his nephew. Sisko blackmails Quark into staying on the station and keeping his bar open. With this resolved, Sisko heads to the surface of Bajor to meet with Kai Opaka, the spiritual leader of the Bajoran people. Kai Opaka prophesizes that Sisko will become the Emissary, a messianic figure of the Bajoran religion, and shows him the Orb of Prophecy and Change, an object that allows him to relive his first encounter with Jennifer.
Sisko returns to the station and meets his new Chief of Medicine, Dr. Julian Bashir, and science officer, Jadzia Dax – a Trill who has the memories of Sisko's mentor Curzon Dax. Sisko has Dax immediately begin researching the Orb of Prophecy and Change. Dax begins a database search, but looks into the orb and immediately finds herself reliving the implantation of the Trill symbiont into her.
Aboard the Enterprise, Miles O'Brien has one last chat with Captain Picard before transporting over to Deep Space Nine for his new assignment. The Enterprise then leaves the station.
Once the Enterprise is gone, Gul Dukat of the Cardassian Union arrives and meets with Sisko. Dukat was the former prefect of Bajor and lets Sisko know in no uncertain terms that he wants his position – and his office – back. Dukat returns to his ship, but does not disembark.
Dax determines that all the orbs came from one location in the Bajor system, so Sisko arranges for Odo to disrupt the Cardassian sensors so that they can explore it without letting Dukat know about their whereabouts. This plan succeeds and Sisko and Dax take a runabout. They move towards the area where the orbs were found and accidentally stumble upon a stable wormhole, the first such wormhole ever found. They are transported to the Gamma Quadrant in a few minutes, a distance that would normally take seventy years to travel.
They fly back into the wormhole in an attempt to return to Deep Space Nine, but they are stopped by the beings that live in the wormhole (the Bajoran Prophets, the gods of the Bajoran people). Dax is returned to Deep Space Nine, but they detain Sisko to determine just what exactly he is…
Dax outlines for everyone else what happened to her and Sisko inside the wormhole. Kira immediately orders the station to be moved to the mouth of the wormhole so that Bajor can claim it before Gul Dukat does. Dukat, for his part, moves on the wormhole himself.
Meanwhile Sisko remains in the wormhole and is engaged in communication with the Prophets through words and images culled from his memory. They do not understand his temporally linear existence and view him as a threat. Sisko tries to convince them otherwise as Dukat enters the wormhole. The Prophets disable the Cardassian ship, close the wormhole entrance, and demand an explanation from Sisko.
As Sisko's conversation continues, more Cardassians arrive and demand to know what has happened to Dukat. Kira informs them that Dukat was swallowed by the wormhole, but Gul Jassad, their leader, does not believe her. He has his ships prepare for battle. Kira attempts to hold them off by broadcasting an illusion to trick the Cardassian ships' scanners into believing that the station is heavily armed, but the Cardassians choose to gamble and attack anyway.
Back in the wormhole, Sisko continues to try and explain why humans value their linear existence using his memories. He shows them the game of baseball to explain why human beings embrace linear existence. They keep bringing him back to his memory of Jennifer's death. When Sisko angrily asks why they continue to do this to him, they explain that it is not under their control and that it is he who is returning to this memory. Realizing that he is constantly reliving the past, the Prophets note that Sisko's existence is not terribly linear after all, something he admits to.
Sisko's runabout emerges from the wormhole just as the Cardassians' attack on the station breaches the shields and Kira is about to give the command to surrender. He is towing Dukat's ship, taking the fight out of the others. Dukat orders them to stand down and the Cardassians retreat.
A few days later Sisko meets with Picard again. He tells Picard that the wormhole aliens have agreed to allow safe passage for ships through the wormhole and into the Gamma Quadrant. He also asks Picard not to seek out a replacement for him because he now wishes to remain on Deep Space Nine, having come to better terms with his grief regarding his wife's death due to his experience in the wormhole. Picard reluctantly agrees, leaving Deep Space Nine in Sisko's hands.