Necessary Evil, DS9 2
Odo takes a page from Law & Order and hunts down clues. A stoles list of Bajorans who collaboratorated with the Cardassians during the occupation in the present, and a murder (plus Odo-as-cop creation story) in the past. It is in the past where we see how Odo and Kira meet.
Turns out Kira first came to DS9 (excuse me, Terok Nor) to pull a hit on one of these Bajoran collaborators. Years later, what must Odo do with this info?
Now is as good a time as any to really tip the hat to Nana Visitor as an actor. Let’s face it, Star Trek isn’t really known for its acting. And some of the acting on DS9 (Avery Brooks and Terry Farrell especially) is really awful. But Visitor, even with that dopey thing on her nose, manages to give very real, unexpected and even subtle line readings. It is really quite an accomplishment.