After the first season episode "Cold Front," this is the best episode from Enterprise's Temporal Cold War arc. It's also the only one not to feature Silik, Daniels, or Future Guy.
That may be why it's so intriguing. Sometimes the arc could seem like it was only there to tease Archer's role in founding the Federation, especially during the third season (the fourth season dumped the arc almost unceremoniously in the two-part premiere). "Shockwave," the season finale/premiere that kicked off the second season, was an opportunity to truly exploit something that had been planted in the pilot, "Broken Bow," but instead was a fairly generic affair that didn't truly explore the potential of the big concept of a war waged across time. That's what made "Cold Front" so intriguing, two agents (Silik and Daniels) dueling with Archer caught in the middle.
"Future Tense" is all about a ship Archer stumbles across and tries to figure out. Sure, the Suliban appear and duel the Tholians (first franchise appearance since the original series, and a precursor to their later appearance in the fourth season Mirror Universe adventure), but the episode is really about exploring the full potential of the Temporal Cold War, especially as it concerns someone who has no idea what's going on, has been caught in the crossfire several times, and would like to finally get some answers. That someone would be Archer. In a sense, "Future Tense" is the last episode you really need to see concerning the arc. It's the one time everything revolves around decisions Archer himself can make. Otherwise you might consider "Detained" the other essential byproduct of the arc, in which the Suliban are explored outside the scope of the arc.
Another interesting element of the episode is the body inside the ship. There's some funny talk about Vulcan-human compatibility, because DNA from both species is found in the body's genes, funny because it seems implausible to these characters, but walks and talks just fine a century later as Spock, not to mention the more sober events from the fourth season. Archer also speculates before anything is known about it that the body might be that of Zephram Cochrane, whose history in Star Trek is more complicated than merely being the inventor of humanity's warp engine. In the original series episode "Metamorphosis," the fact of his having gone missing is finally solved, but at the point of Enterprise is still a great mystery, greater still for his being so central to recent human history. The mating element is an example of the episode being a tad hokey. The Cochrane element is an example of the episode being clever. That's the benefit of being a prequel series. You can have it both ways.
There's also a sequence of repeating time, something that's been done before in Star Trek (the Next Generation episode "Cause and Effect"). It's kept to a minimum but's still another pleasure of the episode. Good fun over all.
franchise * series * essential * character
Memory Alpha summary.
Star Trek The Next Generation Phaser Toy Gun (Google Affiliate Ad)