**** (4 stars out of 5)
Conveniently, everyone of interest to them is there... in the same cell.
One-eyed Klingon General Martok has been interred there for 2 years. It's actually the first time Worf has met Martok for reals, and they quickly become BFFs. Enabran Tain has been held captive since the Unpleasantness in the Omarion Nebula. Oh... and SURPRISE: Julian Bashir. Since before the grim grey uniforms came into use, for over a month, Deep Space Nine's chief surgeon has been a changeling! Long enough to treat baby O'Briens, baby changelings, and do delicate brain surgery on Sisko, anyway.
Garak tells Bashir that sentiment is the greatest weakness of all, but he comes by such terrible ideas honestly: Tain was his father. Though they may only have had one pleasant day together, when Garak repeatedly injured himself learning to ride a hound. (Scrappy Doo is a figure of terror on Cardassia.)
Tain's heart is giving out. The crusty, hamburger-loving, spymaster gushes with pride as he dies: "I should have killed your mother before you were born. You have always been a weakness I can't afford."
Speaking of appalling fathers, Dukat does his best but cannot convince his daughter Ziyal to return home with him. She likes that terrible tailor Garak too much. So Dukat abandons her. Not for the first time. And what's WITH Ziyal? Somehow, half-Bajoran Cardassians have accelerated growth in their early teens accompanied by radical changes in their skulls and faces? (I am, of course, mocking the THIRD actress to play the role of Ziyal in as many years.)
Dax's widow Khan (no relation) invents a method to close the wormhole permanently. But for some reason it fails and "Bashir" looks like the cat that's eaten the riding hound.
The Dominion invades the Alpha Quadrant. "God help us all," intones Sisko. And might I add: YOU ASKED FOR IT! If you'd respected their territory, maybe they would have done the same. Probably not, but you could at least pretend you had the high ground.
"In Purgatory's Shadow" earns those stars. The Bashir Changeling reveal is a great blind-side. The death of Tain is powerful. Over two years building to the Dominion War and it is upon us at last. Hold on to your butts.