On a camping trip in the Gamma Quadrant to conduct a planetary survey report, Sisko, Jake, Nog, and Quark encounter the ruthless soldiers of the mysterious Dominion, the Jem'Hadar.

Chief O'Brien is arrested by the Cardassians for collaborating with the Maquis. However, on Cardassian justice is swift: the verdict is known before the trial even begins, and it's always guilty.

The man most likely to take over as the new Bajoran Kai, Vedek Bareil, is accused of collaborating with the Cardassians during the Occupation.

After suffering an accident whilst traveling through the wormhole, Kira and Dr. Bashir find themselves trapped in the mirror universe first encountered by James T. Kirk a century earlier.

When an addictive implant in Garak's brain begins to break down, causing the exiled Cardassian extreme pain, Dr. Bashir must convince a reluctant Garak to accept his help.

Under increasing pressure from Starfleet Command, Sisko tries to rescue Gul Dukat, stop the Maquis from escalating conflict within the Demilitarized Zone, and prevent an all-out war between Cardassia and the Federation.

When a Cardassian freighter, the Bok'Nor, explodes at DS9, the Cardassians blame Federation colonists in the newly established Demilitarized Zone. Meanwhile, Quark is approached by a Vulcan with an unusual business proposition.

Three legendary Klingon warriors reunite on DS9 seeking Curzon Dax, with whom they entered into a blood oath to one day exact revenge on their sworn enemy. Finding Jadzia to be as worthy a warrior as they felt Curzon to be, they invite her to join them on their crusade.

When a damaged Cardassian ship shows up near DS9, Quark is unexpectedly reunited with his lost Cardassian love, who is now a member of the Cardassian dissident movement.

While hosting her first Trill initiate, Dax discovers a tiny, expanding protouniverse that threatens to destroy the entire Bajoran system.

After discovering a colony in the Gamma Quadrant, Dax and Odo investigate the mysterious disappearance of several colonists. Back on the station Vedek Bareil visits Kira, and Jake gets a job with Chief O'Brien.

While surveying nearby star systems for M-Class planets, Sisko and O'Brien find themselves stranded on a previously unknown colony world where the colonists have adapted to life without advanced technology.

Upon returning from a mission to the Parada system, O'Brien begins to notice the crew acting strange around him and suspects there may be some unknown influence at work.

Chief O'Brien and Dr. Bashir help the T'Lani and the Kelleruns eliminate their stockpiles of deadly biological weapons used in their centuries-long war. However, when both governments decide to make sure no technical knowledge of the weapons remains, O'Brien and Bashir must put their differences aside in the name of survival.

Dr. Mora Pol, the Bajoran scientist who studied Odo when he was first discovered, arrives on DS9 with evidence that he has found DNA signatures similar to Odo's on a planet in the Gamma Quadrant.

Quark feels threatened when a charming con artist arrives on the station and opens up a competing bar and casino on the Promenade. Meanwhile, Chief O'Brien is determined to beat Doctor Bashir at racquetball.

A group of refugees from the Gamma Quadrant travel through the wormhole in search of their fabled homeland, Kentanna.

On the fourth anniversary of his wife's death at the massacre at Wolf 359, Sisko has an unexpected encounter with a mysterious woman visiting the station.

After an attempt on Quark's life, Odo re-opens an unsolved five-year-old murder investigation in which Kira Nerys was originally a suspect.

Grand Nagus Zek assigns Quark to initiate negotiations with a planet in the Gamma Quadrant, the Nagus believes it will help the Ferengi Alliance get a profitable business foothold in new territory. However, the plan is put into jeopardy when Quark's new associate turns out to be more than he appears.

Ensign Melora Pazlar, a new arrival on DS9 with a special gravity-based disability, finds an admirer in Bashir. Meanwhile, Quark receives a death threat from one of his former associates.

Political tensions rise on DS9 when Bajorans board the station with a orphaned Cardassian whom they have adopted.

When a violent plasma storm leads to the evacuation of the station, the remaining crew are overtaken by a group of mercenaries led by a timid Trill named Verad who has plans for Lieutenant Dax.

As Federation citizens are evacuated from DS9, Sisko and a skeleton crew attempt to prevent The Circle and the Bajoran military forces under their control from occupying the station. Kira and Dax attempt to reach the Chamber of Ministers on Bajor with evidence of Cardassian involvement in the conflict.

When Kira is removed from her post aboard DS9, Vedek Bareil invites her to visit his monastery on Bajor to reflect on her next step. Meanwhile, Odo, Sisko, and Li Nalas attempt to discover who is the driving force behind The Circle when they begin arming themselves with weapons from a mysterious source.

When Quark presents Major Kira with an earring belonging to a presumed dead Bajoran Resistance legend, she and Chief O'Brien journey to Cardassia IV in an attempt to free him from from a slave-labour colony. Meanwhile, an extremist Bajoran faction known as The Circle continues to agitate tensions on DS9 and Bajor.