the story: Odo is reunited with the Bajoran scientist who first assimilated him into the world of "solids," and who is now claiming he's found Odo's secret origin.
what it's all about: "The Alternate" has an odd predicament; on the one hand, it's not as good as the second Dr. Mora episode, "The Begotten," and it ends up having too many similarities to the first season episode "Vortex," which also teased Gamma Quadrant origins. Later, of course, we learn that Odo's people are the Founders, who created the Dominion, and as such he really does come from the Gamma Quadrant, but with two episodes teasing it but being otherwise unnecessary to the rest of the series, it's the second episode that gets the short shrift in terms of originality.
Thank goodness it at least introduces Dr. Mora, with whom Odo has plenty of unresolved issues, not the least being barely-concealed resentment and rage, where Dr. Mora still thinks of him as the pile of goo he spent months analyzing without ever once realizing it was sentient...
As an exploration of backstory, "Alternate" still exists in a relative vacuum (other than "Begotten"). While flashbacks, thanks to Lost, became a common element of TV storytelling later, usually this was something told, not showed. Sure, the random element of the past would resurface, but never quite as relevant as Dr. Mora, who literally helped shape the individual Odo was to become.
It's just a shame that the first story the producers came up for him was a virtual duplicate of "Vortex" in terms of misdirection and lack of payoff, which clearly was because the rest of Odo's origins hadn't yet been figured out. There are people (fans of Lost, actually), who think this kind of serialized storytelling is irresponsible, but that's only when, such as with "Alternate," things hadn't just not been figured out, but it's extremely obvious after the fact. Again, once showing a possible Gamma Quadrant origin is fine, and if anyone had bothered, later, to explicitly state the story links, it would have continued to be fine, but that just didn't happen, and then "Alternate" did it again, and eventually filled out the story with needless monster-of-the-week material, the same kind of episodic foot-dragging that filled too much of the first few seasons.
Still, as foundation material, like the rest of the second season, "Alternate" does feature some relevant stuff, so I can't complain too much. Frequent franchise guest actor James Sloyan arguably has his best role as Dr. Mora, besides.
franchise- The episodic appeal of the episode actually detracts from its impact, so I'm not giving points for its standard Star Trek nature. series- If this had been linked (heh) to later Odo developments, it would be more relevant.
- character - Still, excellent Odo material with the introduction of Dr. Mora.
- essential - Again, "Excellent Odo material."
James Sloyan (Dr. Mora)