The second season of DS9 was somewhat sparse in its Odo content. There were various little moments sprinkled into many of the episodes, but only three episodes that focused on him in any major way; this was the last of those. And in this case, there are two other plots sharing the spotlight.
Not that I particularly blame the writers. The pace of making a television show means that one cannot wait for that one great story to pop onto the paper from your head. If all you have is three thin stories, and there's a deadline, then sometimes the only solution is to squeeze those three stories together and make one episode out of them. At least I think that's what happened with "Shadowplay" (written by Robert Hewitt Wolfe, usually one of DS9's finest staff writers). Unfortunately, these three stories do not go together particularly well.
The A story (or, what I assume to be the A story, since it's the one that best fits the episode title) is the one with Odo (and Dax). There is also one about Kira and Bareil, and another about Jake and his father.
Arguably, I would have to say the best one (speaking as an objective viewer) is the Jake story. This is the episode in which he takes his first step out of the shadow of his father, by saying out loud that he does not want to enter Starfleet. When you think about it, this is one of DS9's little defining moments that sets it apart from the other Trek series. We already knew that Jake was no Wesley Crusher (thank the Prophets): he was more or less a "real" kid, smart but no genius, who would rather dangle from a Promenade walkway with Nog than invent a new warp drive. But letting him find a direction other than predictably following in his father's footsteps was a bold and unexpected move at the time (even though it was a while before we got some inkling of what Jake did want to do with his life). My main problem is that this story deserved to be fleshed out and made into a whole episode in its own right, or at least an A story.
The Kira/Bareil plotline is on the other end of the scale, and I believe I would say so even if I weren't an Odo fan. I'm not one of those who claim to have known from the very beginning of the series that he and Kira were meant for each other. Yet I do remember not caring for the romance between Kira and Vedek Plywood, er, I mean Bareil. I always fast-forward through their scenes, especially the one where they smooch repeatedly in a rather unconvincingly "heated" fashion.
As for the main event…well, it is nice to see Odo having scenes with one of the other regulars besides Quark or Kira (much though I love his relationships with those characters). However, in my opinion there is practically no chemistry between René and Terry Farrell, at least not in this episode. The most we see is in the beginning, when Dax teases Odo about the Bolian jumja vendor who she thinks is warm for his form--a possibility that obviously has never entered Odo's mind.
The fact that there is no believable reason for Odo to be accompanying Dax on her science mission does not help. Dax says in her log that Odo is hoping to find clues to his origin; but why should he think that this particular mission might turn up any such clues? At least in "The Alternate", Odo had a definite good reason to go to the Gamma Quadrant. Here, there is just a throwaway line.
Anyway, the mission leads to a planet where Odo and Dax find a village where people have been mysteriously disappearing. It turns out that the village (the buildings, the objects, the people) is made up entirely of holograms. The creator is one of the elders, Rurigan (Kenneth Tobey), who fled there to recreate the culture of his planet after it was taken over by the Dominion. Now the holo-generator is breaking down. Dax fixes it. Yay.
This story feels as if it was slapped together in desperation. There is some sloppy writing: for example, Protector Colyus (Kenneth Mars) acts all surprised when Odo demonstrates beaming out and back, but a few minutes later says that looking for signs of transporter activity was the first thing he tried in his investigation. And why are only people disappearing, not buildings or objects? And why can't Rurigan fix the generator instead of saying over and over that they'll never see the missing people again? The whole concept seems like something that would have been more at home on TNG or Voyager than DS9. Odo's speech to Rurigan about letting the holograms continue to exist would have fit just as well in the mouths of Picard or Janeway.
But the A story does have one saving grace: Odo's friendship with Taya (Noley Thornton), Rurigan's little hologram granddaughter. The two of them have some very charming and poignant scenes together. My favorite is when Taya tells Odo the fairy tale about the evil Changeling, and Odo, surprisingly, gets into the spirit of it, in a mock-gruff kind of way. He would have made a good dad; too bad we never got to see that side of him again (except perhaps in "The Begotten").
Finally, as a goodbye gesture, Odo shapeshifts into an imitation of a spinning top (a toy of Taya's). This is the first time that we saw Odo use his abilities not as a tool of his profession, but as a gift, to make another person happy. It becomes even more meaningful when we recall how reluctant he has been up to this point to show his true form to anybody. For me, this ending makes the whole episode worthwhile.