the story: Janeway and Paris are confronted with a paradox concerning their involvement in the annihilation of a planet's population.
what it's all about: Likely a lot of fans settled their opinion of Voyager not to much on the pilot or the premise and whether or not subsequent episodes lived up to it, but on the second regular episode of the series, which jumped right into a fairly generic Star Trek, high concept story. Now, this would not have been a problem thirty years earlier. NBC wanted cool sci-fi concepts to define Star Trek, not the kind of cerebral material Gene Roddenberry kept delivering. This is not to say that Voyager was incapable of being cerebral, but as the first Star Trek series to air on a broadcast network since the original, it's perhaps not unexpected that somewhere along the way network executives finally got their way. Sometimes.
This just happened to be one of those times. Again, there's nothing particularly wrong with "Time and Again" itself. The closest it has to any significance is the emergence of Kes as a kind of series regular version of Next Generation's Guinan, someone who could sense when something wasn't right. I'm not sure Kes ever quite became another Guinan (not mysterious enough), and there's other material later to sells this version of the character better.
So that leaves us with how well the concept actually works. It's another problem of who they chose to focus the episode around, I think, something that later in the series often fell to Chakotay, who never gets the credit he deserves for selling just about any concept (high point: "Distant Origin"). It was more Janeway's determination than her science background that made her stand out, so having her lead a story like this was one of its weak points, I think.
But on the whole, I think it's a pretty fun experience.
- franchise - The idea of Star Trek featuring cool sci-fi concepts shows up here.
series- Not hugely impactful in this regard. character- Soft start to the evolution of Kes. essential- Not especially.