Dax is reunited with the spouse of a previous host.
This is a solid episode, with a strong concept and decent character moments.
Whenever you watch this episode you have to consider the time it was released and the impact it had on viewers. (Go to the Memory-Alpha web page about 'Rejoined' for details). This confirms the decision to include a same sex relationship to frame a story of forbidden Trill love was the best way to put it across. If Dax was portrayed with a male Trill character, nobody would have been interested, primarily because standard romance stories in episodic television mostly never work.
Personally, I think it is written better than most Star Trek love stories due to the backstory associated with the two characters. However, I still want the romance to fail because Dax is a main character and I do not want the status quo disrupted by her being in a relationship. Plus her most interesting aspect is the importance of the symbiont and the prospect of trampling all over it for a 'romance of the week' is not desirable.
The best scene for me is the dialogue between Dax and Sisko. Trill society does not want an aristocracy emerging and there is a harsh consequence associated with that belief. Here we get the crux of what makes the situation so complicated and it includes strong performances from Terry Farrell and in particular Avery Brooks.
Susanna Thompson is great as Lenara Khan and stands out amongst long line of Star Trek romantic interests for having a fairly interesting story combined with a strong performance.
The background story about the wormhole project feels pretty generic and doomed to fail, but I love the scene where Worf responds to a Klingon related question from the Trill science team.
It's a 7.5/10 for me but I round upwards.