In brief: Entertaining and intriguing, albeit with no possible answers and an indication that the whole arc-to-be is the ultimate paradox plot.
Time travel rarely makes any logical sense, and it doesn't make much sense in "Cold Front," where characters from the future explain to characters in the past that they're trying to keep other characters from the future from altering history from the way it "should" play out. How in the world is one supposed to know the way history "should" play out? If you're a product of everything that came before, how can you possibly exist as any sort of sentient constant that can identify one timeline as correct as compared to another? Even assuming you could exist as a constant that was created from one possible reality, to assume that is the "correct" one is little more than making an arbitrary judgment based on what you think you know.
To be sure, I liked "Cold Front," which is in the spirit of solid entertainment rather than deep significance. I didn't quite love it, perhaps because it lacks the ability to blow us away with truly compelling drama or grounded storytelling. Most of the concepts here are well traveled in Trekkian lore, as is much of the execution and the inherently circular logic. But I liked the underlying spirit: This is, simply, two doses of elusive weirdness and one dose of reaction with heavy trepidation. Captain Archer finds himself completely out of his element, which I found gratifying. Time travel isn't a known proof here as it was on the other Trek shows; to Archer, it's more like science fiction.
The mystery is laid out when crewman Daniels (Matt Winston) comes to Archer and tells him that a Suliban operative named Silik (John Fleck) has boarded the Enterprise disguised as one of the peaceful guests who are on board to witness a nearby cosmic event. Daniels has been a part of Archer's crew all along, but he has apparently never been just an ordinary crew member; he's an operative from roughly 900 years in the future assigned to stop timeline manipulation in the 22nd century. Silik is the Suliban whom Archer fought at the climax of "Broken Bow"; he works for a mysterious entity from the future (but from earlier than Daniels' time frame) who employs the Suliban to manipulate the timeline by proxy.
The Temporal Cold War, according to Daniels, is the struggle involving those possessing time-travel technology — between those who maintain the idea that interfering with the past cannot be permitted, and those who would change history to benefit themselves. Daniels, much to Archer's dismay and amazement, takes the captain to his quarters, where he uses a device that shows how people from the future monitor the intersecting timelines of the past. It's a massive, graphical 3D array of streams, colors, and icons representing, I guess, all of known history.
Scott Bakula's performance is key in his scenes, where Archer's universe is revealed to him as a toy to be manipulated by those who are hundreds of years in the future. Archer is astonished and overwhelmed; Bakula sells these scenes with an understated performance that conveys his surprise through a sort of stunned quiet.
The bizarre irony here is that Archer finds himself in a situation where motivations and consequences go in opposing directions as far as the Enterprise is concerned. Archer's ship is caught in the middle of a mess far bigger than its own role in it. Consider, for example, that Silik prevents the Enterprise from being destroyed in a near-cataclysmic accident (or was it an accident?). When Daniels lays everything out on the table for Archer, the dilemma is complicated by the fact that Silik is allegedly working on the amoral side of the Temporal Cold War ... and yet his mission was to save the Enterprise from destruction. Was history "supposed" to include the Enterprise being destroyed? Daniels doesn't say.
Should Archer even trust Daniels? He obviously has information about things that no one else does. But as T'Pol points out, does that necessarily make him a time traveler? (Up to now, no one in this century has any evidence that time travel really exists; the Vulcans treat the matter with skepticism.) More importantly, if Daniels is a time traveler who says he needs Archer's help, how can Archer know that Daniels is the good guy? Just because he says so? Archer's situation is an impossible one to be in, because he has to make important decisions based on woefully incomplete information. I submit that a big reason Archer trusts Daniels is because Daniels is human. Or, as Daniels curiously says, "more or less" human.
I'm not sure this is a great idea on Archer's part, since manipulation by gaining the trust of those in past timelines would be a perfect way for an operative to change history. In one scene, Archer is confronted by Silik, who makes that very point. Daniels' claims could simply be servicing his own ends, for his own faction in the temporal war. Indeed, how can Archer possibly choose a side in this conflict at all? Damned if you do; damned if you don't.
That question is part of what makes "Cold Front" fascinating. Here's a situation where we're not sure what to make of the players — where the various sides of the struggle are shrouded in gray areas and we don't know what's right or wrong, what's true or a lie, and even if we did, making the right decision could mean the Enterprise "should" end up destroyed. Good luck, Captain Archer.
What's a little disappointing is that the story itself doesn't play this aspect more prominently. It would rather choose to make Daniels our friend and Silik the enemy, and favor a conventional chase premise over more detailed examination of the logical dilemmas. Ultimately we have Silik blasting Daniels into oblivion, and Archer tracking Silik through the ship and walking through walls with Daniels' phase-shifting technology (which is, conveniently, smart enough to know not to let Archer's feet pass through the floor). When Archer has Silik apparently cornered, Archer talks rather than taking action, allowing Silik to slip away, and earning Archer a D-minus for the day in my grade book for intruder capture.
This at least leads to a payoff that is a great visual image, where Silik escapes the Enterprise by opening the launch-bay doors and jumping right out of the ship, floating toward a Suliban vessel waiting to rescue him. Now that's a dramatic escape. I also enjoyed the ominous take on Daniels' quarters, which Archer has sealed until further notice. This is a contrivance to postpone dealing with fallout from this story until the writers feel like it (why wouldn't Archer investigate Daniels' quarters right now?), but at least it's a contrivance done entertainingly, with tones of menace.
Of course, there's one other underlying issue to briefly discuss, which is that the Temporal Cold War could be held up as an excuse for explaining away things on Enterprise that contradict events that happened on the previous series. Are we witnessing a sly device the writers have created to let themselves off the hook for things they might contradict? Nah, probably not — the canon timeline would inevitably be the same one as created (or altered, wink, wink) in this version of the past. Unless, of course, the writers themselves have beamed over to another reality.
In any case, something like the Temporal Cold War is a nightmare for logicians and a paradise for those who enjoy paradoxes. Perhaps we should just concede that if it's entertaining, it's effective.
As for anyone who claims to pass through centuries of history in an effort to keep the timeline "right," I hereby submit them as another Trekkian puzzle for the Timeline Gods to sort out.