Nutshell: A bit repetitive and obvious at times, but the dialog works wonders with the characters.
"The Ascent" is a premise based on a bit of a cliche—the idea that two adversaries must put aside their differences in an effort to work together to survive. It hardly matters. A show like this is not about whether or not the characters will succeed; it's about what the two characters learn about one other and themselves in the process.
Like many Trek episodes, "The Ascent" is divided into two stories: an A-story that proves somewhat urgent crosscut with a B-story that is little more than entertaining fluff. Behr and Wolfe have successfully balanced these two stories together. While a silly B-story can often sabotage the efforts of an A-story, this doesn't happen here. Instead, the crosscutting between the story lines actually helps draw the situation into something that seems like the many days it's supposed to be rather than the much shorter period that the constraints of a one-hour time slot tends to make it feel like.
It's hard to believe "Let He Who Is Without Sin..." and "The Ascent" were both written by the same two people. The two are virtually antitheses of one other based on a similar structure. Both are situations based on dialog and relationships, but where the former episode failed miserably, here it works extremely well. Part of it, I think, is in the nature of the relationship. Trek tends to drop the ball when it comes to exploring relationships between men and women. There is too much emphasis on standard cliches and sophomoric sex jokes. And usually things feel forced, not genuine.
On the other hand, the relationship here—between Quark and Odo—represents character interaction at its finest. The dialog is sharp, acerbic, and genuine. It's sensible and credible, because it's based on a relationship built during the past four years of DS9's run. (The relationship between Dax and Worf, on the other hand, was built in four minutes.) Most importantly, it adds up to something, because in the end both Odo and Quark come to realize some new things about themselves and one other.
The episode opens as Odo arrests Quark, announcing that it's the day he has been waiting for the past ten years. Quark has been summoned to appear in Federation court in connection with a shady, subversive group known as the Orion Syndicate. (It's of great irony that Quark, much to Odo's surprise, later turns out to be a witness, not a suspect, in the Orion proceedings.) While in a Runabout en route to Federation court, a bomb on board set by the Orions to assassinate Quark explodes, forcing Quark and Odo to crash-land their shuttle on a frigid, rocky planet. (Scratch yet another Runabout—do these things even survive long enough to get names any more?)
They have minimal rations, no supplies, and the damaged communications system can't permeate the atmosphere. The only option is to begin the ascent—to carry the comm panel up a nearby mountain such that they might be high enough to get a signal out, before they either freeze or starve to death. In the meantime, they must rely on one other, and have little to do but talk and climb.
Since its genesis, the relationship between Quark and Odo has been something that requires a decoder ring, and that's perhaps why it's always been so interesting and entertaining. These two guys obviously don't hate one other; in fact, they probably wouldn't be complete without one other. It makes me wonder if Odo would truly be happy to catch Quark and send him away after ten years of pursuit. What would he do without Quark to keep him on his toes? At the same time, what fun would Quark's silly scheming plots be without Odo looking over his shoulder?
No, these two aren't enemies, they're merely rivals. Still, calling their rivalry "friendly" would probably not be accurate. Each gets genuinely annoyed when the other's actions disturbs his work schedule. But underneath the constant insult-trading, posturing, and threatening lies two people who know they're friends of sorts, but also know that their friendship is something that can never be voiced verbally. They must talk in code and never spell out their true feelings—because that's just the way their relationship is. The closing scene of the episode is great because it highlights this: The two characters verbally "confirm" their hatred of one other... but then break into a chuckle that reveals all.
And that's what "The Ascent" is all about. It's about these two friends and the way they never have, and probably never will, admit to their friendship. When mixed with sharp dialog, highly commendable performances and believable characterizations, these two personalities highlight what an asset to DS9 as a series these types of relationships are—it's the type of thing that defines the show. Plot lines come and go, but the characters are the real permanence, and the way "The Ascent" reminds of this is priceless—it's the reason fans tune into Star Trek week after week.
So as tensions mount and the situation looks bleak, a physical fight between Odo and Quark ultimately ensues. While this is perhaps an overly obvious result and it conveniently allows the added plot twist of Odo breaking his leg after an accidental roll down the slope, it's one of those things that just had to happen sooner or later for the sake of completeness.
What the rest of this story line is about is survival. The climb is a towering task entailing more than a week of walking, and after Odo breaks his leg, Quark has to build a stretcher and carry him up the mountain the rest of the way. Without food, heat, or supplies, this is nearly impossible. After briefly giving up several times, Quark somehow makes it high enough to get the signal out. That's perhaps a given, but the way the episode conveys the trip is respectable, despite the repetitive nature of the plot. Thanks to some strong performances and decent technical work, there wasn't a moment I didn't believe the two characters weren't really on a mountain, freezing, tired, and starving.
The light but identifiable B-story centers around Nog's return to the station, now a sophomore cadet assigned to field study. Jake moves out of his quarters with his father and into new quarters with Nog. Nog, however, has been changed by the academy. He is now very disciplined but also extremely (for lack of a better expression) anal-retentive. Jake is a laid-back slob. Can you say roommate problems? This is something I can understand based on personal experience and the testimony of many acquaintances.
Sisko gets some amusing little moments in the plot, as his talk with Rom about their respective sons proves enlightening (although Rom's admittedly amusing gag of thinking his son's behavior change is because he has been replaced by a Changeling impostor does little to alter my recently-voiced opinion that he's a dimwit). My favorite line, however, comes near the end, when Sisko lays down the law concerning the two's rooming squabbles: "I know you can make it work, because I'm your captain [to Nog] and I'm your father [to Jake], and what I say goes [to both]. Good day, gentleman." The notion is very amusing... and is extremely Sisko.
"The Ascent" is a character episode all the way—classic DS9.