Nutshell: Sparsely amusing but mostly just rambling and pointless. Near-zero substance.
"Darkling" is about as superficial as they come, but unlike the also-shallow "Blood Fever," there's no reason for any of the events here to happen, nor the possibility of consequences to emerge from any of the characters' actions. Things simply happen because the writers apparently thought they would be "fun." Whether that's intended fun for them, for us, or for the actors I'm not really sure, but I am sure about one thing: You can't base an entire episode on one silly (and I do mean silly) concept lacking all dramatic relevance and expect it to sustain an hour.
There's not really a story here—it's simply a premise that can be explained in a single sentence, which is then used for wackily glib characterization: Doc tries to expand his personality by using data from holodeck characters, but when his program malfunctions, an "evil" personality emerges and terrorizes Kes.
Mired in here is a theme about Kes reaching a "crossroads" in her life (she has fallen in love with this week's friendly, all-too-human alien and considers leaving the ship to pursue a relationship)—a storyline that doesn't have nearly the genuine emotional sense or time devoted to it that it demands. There's also a "mystery investigation" plot angle when Kes' new boyfriend (Lee Smith) is injured after being pushed off a cliff by a shady character in a hood.
Well, no points for guessing that it was Evil Doc that assaulted him—if, for no other reason, because the previews gave away that Doc was going to be a bad guy this week. (Although, more amusing is the hypothetical situation that this hooded character is really a jealous Neelix stalking his ex-girlfriend.)
Speaking of Neelix and Kes, "Darkling" finally confirms that the confusing "breakup" in "Warlord" was actually not a side effect of the alien possession of Kes' body. In retrospect, the handling of the whole idea is poor; then again, I really don't care, because it also means I don't have to sit through any more silly scenes between the two characters.
The episode follows by-the-numbers plotting as Doc switches between Jekyll and Hyde while his program malfunctions for reasons Torres can naturally explain with her technical prowess. (The Hyde, if I may say so, is Doctor Hyde—quite handy with the hypo-spray, to which Torres can later attest.) There are some surprisingly amusing, mildly macabre moments within the confines of the script's banality, as Evil Doc cripples Torres with some creative uses of sickbay drugs. And the episode's best scene features Evil Doc's trek from the sickbay to the holodeck—simply allowing us to watch his quiet, repressed insanity in the everyday situations of walking down the corridor and riding in the turbolift. Paul Baillargeon's ominous score sets the mood wonderfully.
Unfortunately, this idea doesn't have far to go. It doesn't take long before the mild amusement of Evil Doc's unstable mindset begins to run out of steam, and we're then treated to the standard plot device of his kidnapping Kes. Evil Doc beams himself and Kes down to the planet surface to await transport off the world for motives that are never clear. There are indications that Evil Doc feels compelled to "protect" Kes from something, but Menosky's script never bothers to explain why.
I don't have as much problem with the pedestrian plot as I do with the fact that every idea within it contains virtually zero substance. Just about everything Evil Doc does and says is meaningless. None of the dialog reveals any relevant character insight or theme. And don't even try to label the scene in Byron's bar where Kes and the Doctor discuss the benefits of "good" as decent writing or character depth. It's not. It's a pretentious smattering of false positive emphasis, as if a pile of "Roddenberry values" were stacked next to a barrel of TNT and left to explode onto the television screen. (One of my friends sarcastically commented that, by coincidence, his next psychology paper was concentrating on the exact topics Kes was discussing. I wished him good luck.)
Likewise, if we're supposed to take Kes' character arc seriously, then there needs to be a point to it. We all know she won't leave the ship anyway, so unless the writers devote some time to analyzing what Kes' options are and the relevant benefits and regrets each would bring, there's really no reason to bring it up. Unfortunately, this story is ultimately not about Kes. Once the writers introduce the topic of her dilemma, it's quickly abandoned in favor of the "crew member behaves erratically" paradigm. Kes' problem is short-changed to the point we don't care; all that remains are its uses in the plot machinations and a standard tack-on in the episode's coda explaining "why" she has decided to remain on board Voyager. Not good, folks.
The ending contains a nifty special effect: when Doc throws himself and Kes off a cliff, Voyager beams them up as they're falling to their doom. Unfortunately, this fresh visual hardly justifies the rest of the hour. The implications of Evil Doc's final actions sums up just how unfocused the entire show is. It tries to be "fun," yet it contradicts any possible theme of Evil Doc trying to "protect" Kes.
Menosky seems to enjoy episodes where characters act outside the normal range of reality (TNG's "Masks" and DS9's "Dramatis Personae" come to mind). But with "Darkling," Braga and Menosky have nothing substantial upon which to form any fresh ideas. Menosky's use of "evil" as a theme is merely perfunctory. The result is a story that rambles with no discernible direction. Doc's interactions with the crew are limited, missing opportunities that could've been interesting. And the few times his personality does switch between Jekyll and Hyde aren't used for any dramatic effect but simply for the convenience of the plot.
The overall product seems to be little more than an excuse to give Picardo some varied "acting" scenes, some of which work nicely, others which fall flat. Sure, Picardo may have had fun, but that's not much of a rationale for an episode.
"Darkling" is watchable, but nothing more.