Star Trek Deep Space Nine Feature Length Episodes: Ranked
4. In Purgatory's Shadow/By Inferno's Light
Another Garak focused episode, this installment revolves around his search for survivors of the joint Cardassian/Romulan invasion fleet. He travels into the Gamma Quadrant with Worf but they are quickly taken prisoner by the Dominion and brought to Internment Camp 371.
There, they are met by the Klingon General Martok, finally appearing in the flesh. They also find Tain, Garak's mentor and, his colleagues discover, his father who is dying. But most shockingly, they discover Dr. Bashir, who had been replaced on the station by a Changeling.
On the other side of the Wormhole, DS9 is readying itself for war. Dukat reveals that Cardassia has joined the Dominion, giving them a foothold in the Alpha Quadrant. The Klingon Fleet, commanded by Chancellor Gowron, arrives at DS9, unable to hold back the Dominion and Cardassian forces. Starfleet reinforcements arrive along with a Romulan task force, undoubtedly looking for revenge.
It is a breathtaking story that rockets along. The Dominion are finally revealed as the major threat that has been promised, Cardassia revels in its villainy and, across the Galaxy, Worf battles soldier after soldier in fights to the death, sparing his friends the pain.
There is a small plot hole in the episode (why did they leave the Runabout in orbit?) that is addressed later in the series. But, minor quibbles aside, these episodes showed that the writers were taking the gloves off and war was on the way.