the story: Via sci-fi plotting, the crew meets its own descendants, in the present.
what it's all about: This is one of the Deep Space Nine standalone episodes ("The Visitor" was another) that left a definite impact on the later franchise, later echoed in Voyager's "Endgame" (its final episode) and Enterprise's "E2." So as a matter of historic significance, "Children of Time" already has a lot going for it.
While the idea of technobabble that sends the ship back in time and creating, in essence, an alternate timeline for the characters and whole generations of successors who meet them in the present, just before the technobabble that made it possible in the first place is itself pretty fascinating, none of it would matter at all if there weren't an emotional hook to it, and there is. That's my biggest problem, at least with Star Trek, and maybe storytelling in general, in that I'll certainly accept a nifty idea, but if it doesn't have any depth, I see very little reason to care too much about it. There's at least one episode I've docked as one of the franchise's worst (Voyager's "Twisted") because of that kind of lazy storytelling.
So anyway, the emotional hook is especially good because it basically push forward, at long last, after a series of fits and starts, one of its biggest narrative arcs: the relationship between Odo and Kira. There were times during this season where I thought the writers had somehow forgotten it ("A Simple Investigation" is the most egregious example), even though it was hugely important so many times in the past. Perhaps somewhere along the line someone decided Odo had abandoned the idea as impractical, and needed a reason to revisit it, which is what 'Children of Time" is in a nutshell.
Being a changeling, Odo is one of those fictional characters who either ages very slowly (as Vulcans and Klingons demonstrably do) or not at all (Odo). As such, he's the only original crew member who's still around in his original form from the technobabble problem. That essentially makes this an Odo episode, even though most of it really spends times exploring other aspects of the plot. Like Janeway in "Endgame," he's become obsessed with the one person he most regrets losing, which is of course Kira, and eventually makes a huge decision that not only conveniently provides a giant reset button (the noble crew had opted to go ahead and duplicate the original technobabble problem and in effect sacrificing their own futures so that the people who ended up existing because of it can continue to do so), but makes it clear, beyond any doubt, that this was an Odo/Kira episode all along.
It's refreshing, really, because these are the two characters who were least allowed to explore the true magic of the series otherwise, usually confined to the most miserable, mundane elements. Sure, they weren't Starfleet officers (neither were Jake or Quark), but surely they could experience some fun, too? So this is their big moment. I mean, their big moment.
And from this point onward, they were truly on the inevitable path to romance, because they no longer had doubts about what they meant to each other.
- franchise - Later series borrowed the basic template.
- series - For a one-off episode, it ends up reflecting the course of Deep Space Nine well.
- character - It's a Kira/Odo episode by any other name.
- essential - Unlike any other experience they had together, and that's an extremely good thing.