This sequel to third season's "Through the Looking Glass" is an unabashedly simplistic comic book adventure featuring the Siskos in the mirror universe. Ben, Jake, and the other Jennifer (Ben's widow in the other universe) find themselves in a shoot 'em up Star Wars like story that puts subtlety and character development on hold to celebrate Star Trek's space-pirate side. The adversaries, seen in the B story, are Worf and Garak, giving Michael Dorn and Andrew Robinson a chance to ham it up and quote Darth Vader (and Captain Picard). The whole episode features cookie cutter storytelling (like the original Star Wars) as we cut back and forth between both sides, with everything leading to a big space battle at the end that has (appropriately) special effects that rival the early Star Wars movies.
Unfortunately, while the mirror universe setting was fresh and exciting when it was introduced in 1967, by this point it's no longer such a novel idea. The three Siskos have a chemistry together, and perhaps it might have been more interesting to see them sharing a more emotional adventure in the normal universe. Just imagine how weird it would be to see a Ben/Jennifer/Kassidy love triangle!
The mirror universe would get a rest in the fifth season before coming back into play in sixth season's "Resurrection".