For my money, Deep Space Nine's Sixth Season was the series' best, and that is quite a distinction. The show tells stories in this season that are both more epic and more personal than ever before, features genuine twists, great acting, of course, as well as some infinitely memorable moments.
The season begins with a sensational story arc that picks up where season 5's "A Call to Arms" left off. The arc is perhaps the show's best, and brings about many developments: Nog becoming an officer, Gul Dukat's daughter getting killed by his second-in-command, Starfleet retaking the station. The show then segues back into its blend of character-based drama and war tales that make this season so good. Character stories are plentiful here and include: Worf and Jadzia tying the knot in "You are Cordially Invited...", Bashir being reunited with his not-quite-so-well-adjusted genetically engineered friends in "Statistical Probabilities", and Dukat's truly evil nature being exposed in the terriffic "Waltz". Marc Alaimo delivers an astonishing portrayal of the once-proud Cardassian Military Leader now a schizoid, hallucinating, paranoid man driven hopelessly mad by his beloved daughter's death. The highlights continue with "Far Beyond the Stars", an episode on race relations on Earth, circa 1950, that has echoes of TNG's "The Inner Light". But where that episode was warm, this one is painful and uncomfortable, but unmistakeably brilliant. It even ventures into the metaphysical, onto the nature of perception and dreams. A memorable episode. Sisko also had some important development in "The Reckoning", where we truly begin to see how great the changes in his soul have become when he is willing to be an Abraham to save Bajor. There were plenty of other character-driven episodes. Chief O'Brien befriends a criminal in "Honor Among Thieves", Kira learns the horrible truth about her mother in "Wrongs Darker...", and Bashir is recruited into a ultrasecret intelligence agency in "Inquisition", which brought us the first glimpse of the amoral Section 31 group, and "Tears of the Prophets" has the most shocking plot twist of all, with Dukat becoming indwelt by a Pah-wraith and murdering one of the crew, as well as the disappearance of the wormhole. There were also plenty of lighter moments. "His Way" introduces the very popular Vic Fontaine hologram who helps Odo out with his love life. "The Magnificent Ferengi" has Quark, Rom, Nog, Brunt and various other Ferengi attempting to free Quark's mother from Dominion incarceration. "Who Mourns for Morn" is the only episode dedicated to everyone's favorite barfly, "One Little Ship" is a cheeky tribute to old science fiction shows where people become miniaturized.
This season also includes my personal favorite episode. "In the Pale Moonlight" is undoubtedly the most spectacular episode that the show ever created. For an episode where nobody leaves the station, nobody gets in a firefight and without even a single scene of space combat, some might wonder how this could be the best episode, let alone one of the most exciting. It is both, in my opinion. The episode centers on Ben Sisko's attempt to gain the Romulans as allies in their fight against the Dominion. In order to do this, Sisko fabricates internal Dominion files, trades a potentially lethal substance for an essential data rod, and becomes indirectly responsible for the death of a Romulan senator. However, the plan soon gets out of Sisko's control, and he must continue down the road paved with good intentions. The episode is beautifully paced, with several twists and a great sudden reversal at the end. One must marvel at the choice that Sisko had to make: save countless lives and compromise your moral integrity or don't and suffer the consequences. A thoroughly nuanced and powerful hour of television, with Avery Brooks' most powerful performance in the run of the show. After watching this episode, it is easy to see why most DS9 fans hail him as Star Trek's best captain. Andrew Robinson as Garak also turns in a memorable performance.
In short, the highlights of this season are too plentiful to list. Buy it.