Nutshell: Weird, labyrinthine, goofy, bordering on nonsense ... and quite fun.
The plot of "Relativity" is like some sort of comic maze. By the end, the madness has grown so absurd that the characters can barely restrain their grins of bemusement. This is Star Trek sci-fi on crack.
I liked it. It's fun.
"Relativity" begins with some suspense and intrigue; then it proceeds into an explanatory plot-revealing mode with dialog-based story advancement and manageable action; and finally it just turns into sheer lunacy, as the timeline leaping exists for the sake of itself, having little rhyme or reason.
As time-travel shows go, the attitude in "Relativity" probably most resembles TNG's "Timescape." The movement through timelines isn't used to put characters at points in history where they must save the world, Federation, etc.; it's more like an elaborate means for jumping around on the stage known as the starship Voyager. The goal: prevent Voyager from being destroyed.
You see, a saboteur of unknown identity has planted a device on the ship. But it exists in a different temporal phase that only Seven of Nine, with her special Borg ocular capabilities, can see. This leads the crew of a 29th-century time ship to recruit Seven for the mission to find the device before it causes a "temporal explosion" that will destroy Voyager. (Why not just a regular explosion? I suppose because a temporal explosion sounds more complex and interesting.)
The 29th-century time ship, the Relativity, is captained by the same man who set the events of "Future's End" in motion—one Captain Braxton (now played by Bruce McGill), who had found himself trapped in the 20th century for 30 years because of his encounter with Voyager. Perhaps to say Braxton set those events in motion is not accurate. If I've learned anything from "Relativity," it's that one cannot utilize traditional logic when it comes to timeline manipulation. This episode deals a lot with that reliable sci-fi chestnut: the time paradox, which renders obsolete our sense of cause and effect.
Do I really need to explain all of this? In a nutshell, Seven jumps back to a point where Voyager was in dry-dock and looks for the hidden bomb. It's not there, so she is retrieved through time again and sent to a point later in Voyager's time frame. While on this mission through time, Seven also must contend with what Braxton calls "the Janeway factor," which is Janeway's tendency to interact with events that are taking place across the fourth dimension, and thus causing annoying "temporal incursions" that 29th-century time ship captains like Braxton must set right.
The story's central twist is that the saboteur turns out to be a future version of Captain Braxton himself. Apparently, he's gone quite mad in the future and has decided he must destroy Voyager—thereby stopping Janeway from ever again infecting the timeline. (The subtext within the idea of Voyager damaging the timeline so often strikes me as the writers taking a jab at themselves for using so many time-travel storylines.)
A story like this depends on execution more than anything else. "Relativity" executes well. It's nothing particularly brilliant, but it's a fun yarn to watch unfold. If you have a short attention span, "Relativity" will not try your patience. The story moves along swiftly and, dare I say, confidently. There's a cavalier attitude here concerning time travel, but the writers approach the material with a light tough that seems to keep the focus on fun rather than making the story a plodding mess. That's a good thing, since any attempt to use common sense in approaching the plot is virtually useless.
Honestly, by the end of the hour's mania, there's not really much motivation behind the timeline jumping. The writers resign the game to a fairly standard chase, where the playground is simply the various timelines utilizing the standing Voyager sets. Braxton goes back to Voyager of season two; Seven follows. Braxton jumps into Voyager of season five; Seven follows. And once Seven stops Braxton, the games still aren't over. Now the damage to the timeline must be repaired as best possible, which means the time ship crew must recruit Janeway (because Seven has already jumped through time too many times and her health may be threatened) to go back in time and stop Braxton from ever having done anything in Voyager's past in the first place. (First place, last place—do these terms mean anything?) Upon Janeway accomplishing this goal, this means Seven will never have a need for visiting Voyager several times in the past and altering the timeline. That means, I suppose, that the whole episode never really happened—or it sort of did, but not really, but ... does any of this make sense?
Aw, hell—Seven's next stop might as well have been November 12, 1955. I doubt it would/would've/will made/make much a difference to this craziness. (Of course, it might matter if that date is actually the key to the space-time continuum the way Emmett Brown theorized.)
I have a question, though. If the people of the 29th century have so much control over time, why does any of this plot even matter? Why couldn't Braxton be retrieved through time before he spent those 30 years in the 20th century? (For that matter, it was my understanding, based on the concluding scene of "Future's End, Part II," that Braxton's fate had somehow been reset such that he never really got trapped in the 20th century at all—of course, I didn't really understand it then, so I suppose I shouldn't try to make sense of it now.)
For that matter, what exactly is the motivation for Braxton blowing up Voyager? To see an end to Janeway's interference with the timeline? If that's the case, why doesn't he blow up Voyager in the past (from our perspective, that is), before Voyager corrupted the timeline in the first place—rather than waiting until the point we call "late season five"? That would presumably prevent him from ever having been trapped three decades in the 20th century. You know, I could go on, but your head would explode.
I think the point of all this madness, if there is one, is that the time paradox has no discernible cause or effect, and that trying to establish cause/effect is simply pointless. Rather, what characters must do in such situations is go with the flow and hope the game plays out the way it "should." I don't know who plays God in alleging to know what the "correct" timeline is, but I would hope those people are well trained and less prone to manic treachery than Braxton. Or, at the very least, I hope they're arrested in advance for crimes they're going to commit. (Heh.)
It's probably a good thing the characters can barely keep all the paradoxes straight, so that at least we as viewers are on the same level as some of the people in the story, like Janeway, who simply wants to be done with the ordeal before it all gives her a headache.
Beyond playing with paradoxes, "Relativity" is sold on its whimsical attitude. It knows better than to take itself seriously, and has some neat scenes involving "shattered" time. My favorite has to be the ping pong tournament, where Paris slams the ball and it freezes in midair for a few seconds before continuing on its way. What does Official Scorekeeper Neelix do after this bizarre event? Why, he scores the point, natch. Hee.
This episode also brings back that long-forgotten Lt. Joe Carey (Josh Clark), unseen for four years. Where has this guy been? It's interesting to note that he appears only in scenes involving Voyager's past, and not in the present. I, for one, would like to know where this guy has vanished to. Maybe the space-time continuum simply swallowed him up.
What the space-time continuum does not swallow up in "Relativity" is the enjoyment factor. This is an episode that's fairly loony, but it embraces its illogic and moves forward with no fear of the future—or the past, or the present.