After seeing a really good episode, I've come to accept that maybe the duds are a...
"Necessary Evil"
Again with the bad titles. This one sounds like a Chuck Norris movie. But it's actually quite the noirish thriller, with Odo playing the Bogart role. And it's a way, way more ambitious episode than I'm used to seeing, with several flashbacks telling the story of a parallel investigation. The best part is, it really delivers.
I loved the noirish feel of this one--you had Vaatrik, the femme fatale, and the flashbacks to the Cardassian days were suitably dark. In flashback Kira you had another femme fatale, with Dukat as the menacing authority figure who knows more than he lets on, and Odo as the sharp investigator who knows less than most of the other players, but figures things out as he goes on. Very Maltese Falcon.
I wonder how much work it took for them to stage the usual sets to make them look sufficiently Cardassian. They definitely turned the lights down, which worked really well.
Without a doubt my favorite moment was when Odo pulled a Columbo while interviewing Mrs. Vaatrik. When he started moving to the door, I said to my wife, "I hope he does a Columbo," then he did the turn and, "There's just one more thing...." Freaking awesome. I read on MA that the writer also wrote for Columbo, and it was a great homage, made all the more poignant by Peter Falk's recent passing.
It was interesting to see Odo's first meeting with Dukat (well, second meeting), Kira, and Quark--there's nice foreshadowing in all of them. It seems obvious to me that this is where he started to develop feelings for Kira.
Even Rom gets to step things up. Turns out he's a total prodigy. He also makes a great whine/moan/scream sound.
The only thing I would have changed would have been having Quark's eyes closed when he was comatose. Something about them open made it look kind of silly.
But this was, for me, just about a perfect episode. At first I was afraid it was going to be the usual "someone gets taken over by an alien and commits a crime"-type investigation, but it turned out to be an actual human story (ironic again, since none of them, were human) that was well played by everyone.