"Emissary" is the series premiere of the American science fiction television series Star Trek: Deep Space Nine. It was aired as a single two-hour episode on its initial broadcast, but was divided into two one-hour episodes when it aired in reruns.
Set in the 24th century, the series follows the adventures on Deep Space Nine, a space station located near the planet Bajor, as the Bajorans recover from a brutal decades-long occupation by the imperialistic Cardassians. In this premiere episode, Commander Benjamin Sisko (Avery Brooks) and his son Jake (Cirroc Lofton) arrive with Starfleet personnel on the station shortly after Cardassian occupation forces have departed. While working to repair the station and assist the Bajoran people, Sisko discovers an unprecedented wormhole connecting Bajor to the distant, unexplored Gamma Quadrant of the galaxy and the mysterious, incorporeal beings that inhabit it.
Plot
Part I
During the Battle of Wolf 359, Starfleet is under attack by the alien hive mind known as the Borg, which has temporarily assimilated the human Starfleet captain Jean-Luc Picard. The battle is a rout, and Commander Benjamin Sisko orders his crew to abandon ship. He rushes through the crumbling ship to find his son Jake and wife Jennifer. He saves Jake but finds Jennifer is already dead, and is forced to leave her behind as the ship is destroyed.
Three years later, Sisko is assigned to command space station Deep Space Nine in orbit of the planet Bajor. He finds the station in ruins with many inhabitants leaving and the rest struggling to rebuild the station. Bajor has won independence from Cardassian occupation and invited Starfleet to assist in their recovery, much to the disgust of Major Kira Nerys, the station's Bajoran first officer. Sisko strongarms the Ferengi Quark into staying on at the station. Meanwhile, Sisko is contemplating resigning from Starfleet. He receives orders from Captain Jean-Luc Picard — he is to prepare Bajor for membership in the United Federation of Planets — and can barely contain his hostility toward the man he blames for Jennifer's death.
Desperate to unify a Bajoran people whose government is on the verge of collapse, Sisko visits the Bajoran spiritual leader Kai Opaka, who shows him an orb that the Bajorans believe was sent by their gods, "the Prophets". Opaka calls Sisko the "Emissary" and tells him he is destined to discover the Prophets' home, the Celestial Temple. Sisko's science officer, Lt. Jadzia Dax, determines that the orb is connected to mysterious phenomena in the nearby Denorios Belt.
Sisko receives an unwelcome visit from Gul Dukat, the Cardassian former commander of the station; Dukat unsubtly makes it clear he's looking for the orb Sisko was given. Seeking to investigate the Denorios Belt without the Cardassians following, Sisko concocts a ruse that allows the station's security chief, Odo, to temporarily disable Dukat's warship.
Part II
Dax and Sisko investigate the Denorios Belt in a runabout, discovering a wormhole leading to the Gamma Quadrant on the opposite side of the galaxy. As they attempt to return, Dax is teleported back to Deep Space Nine, while Sisko remains in the wormhole.
Kira, recognizing the wormhole's value, orders the station moved to its mouth. Dukat enters the wormhole, but the station's staff are unable to follow, as the wormhole seemingly disappears after Dukat enters it. Cardassian ships arrive to investigate Dukat's disappearance, assuming he has been killed. Disbelieving Kira's claims about the wormhole, they order Kira to surrender DS9 or be destroyed. Kira bluffs that the station is heavily armed.
Sisko encounters entities in the wormhole who have no understanding of corporeal and linear existence. When Dukat's ship attempts to pass through, they close the wormhole, irritated by the presence of corporeal lifeforms. When Sisko attempts to explain linear time, the entities point out that he continually returns to the moment of Jennifer's death. Sisko realizes he is "living in the past" by not moving on from his grief.
The Cardassians attack Deep Space Nine, but as Kira prepares to surrender, the wormhole opens up, with Sisko's runabout towing Dukat's ship from it, and the Cardassians stop their attack. Sisko reveals that he negotiated with the wormhole aliens to allow ships to pass through. Later, Sisko informs Picard that he plans to remain in Starfleet, letting go of his anger and making peace with Picard, who wishes him luck.