Nutshell: A 100% typical exposition on the "dead captain" theme. No, thanks.
"Coda" is an episode based on an idea that has been done many times before—and much better—on Trek. The general idea is to temporarily kill a major character—in this case the captain—and milk it for all the emotional pathos it's worth.
Personally, I think I've seen this story rehashed enough times already. If you want a really good example of this theme, then you should watch DS9's "The Visitor," a tour de force on just about every level. "Coda" has none of the resonating emotion or epic moments that "Visitor" had. I think the overall problem is that once "Coda" figures out where it's going, it unfolds completely as expected and never comes close to being anything but pedestrian.
That is, of course, only after it has found its direction. The first two acts of the episode bombard us with a multitude of different ideas out of the Trekkian bag of tricks. Shortly after the episode opens (after a completely routine Neelix scene that has me suspecting we won't likely see a new Neelix come out of the recent "Fair Trade"), Janeway and Chakotay take a shuttlecraft to the surface of a planet (for reasons that are never explained). Well, no points for guessing that the shuttle gets caught in a storm and crashes, a la the unfortunate reversion to the reliable second season cliché: In the event that a premise cannot be created from a fresh idea, simply crash another shuttle and put the characters into a tough situation that way. (What is this, the fifth shuttle the Voyager crew has lost? Perhaps sixth? I've lost count.) Janeway is critically injured in the crash, but Chakotay revives her; then the two are attacked and killed by some Vidiians, at which point the scene cuts back to the shuttle where the sequence of events repeats.
At first, I figured we were in for a rehash of the time loop story—something along the lines of TNG's "Cause and Effect." The sequence begins again, but differently. This time the Vidiians attack and destroy the shuttle. Repeat again. This time Chakotay pilots the shuttle back to Voyager, where Doc reveals that Janeway has contracted the Vidiian Phage and is suffering from symptoms which caused her to hallucinate the time loop. After working 40 hours searching for a treatment, Doc gives up and tells Janeway the only humane choice is euthanasia. Practically before she can protest, he kills her with a toxic gas.
Cut back to the shuttle with Janeway and Chakotay and... well, I think you begin to get the idea.
As these events progressed and reality continued to get more confused, it seemed anything was possible. My curiosity began to percolate at this point, because the episode was just acting so weird. But just as things start to get interesting, the plot settles down into an unimpressive "exposition on Janeway's death" direction that proves less than compelling because of its predictable plot advances.
Basically, the plot boils down to a standard ghost story in which Janeway dies but her "spirit" (or whatever you wish to call it) remains to observe the crew in the aftermath. How do we know she's a spirit? Because her long-deceased father (Len Cariou) appears out of a white light and tells her she is, that's why. Janeway, being a scientist and skeptic like her father taught her (one of few nicely drawn ideas from a past episode, "Sacred Ground"), looks for every other possible scientific "phase shift" and "dimensional displacement" explanation to fit the situation.
Some of the individual ideas that Jeri Taylor's script throws us are nicely handled and performed. The idea of Kes sensing Janeway's presence with her unique mental abilities makes sense and supplies the plot a needed momentum boost. And Janeway's inability to accept that now that she's dead and her crew will go on without her is relevant, even if completely derivative.
The obligatory funeral scene is a shameless and manipulative attempt to tug at the emotions. Though somewhat necessary given the story's specifications, it feels at times like an annoying kid tugging at your sleeve. Actually I sort of liked it in a way. It made for an intriguing "what if" scene; I'm sure that, deep down, all of us have wanted to be the proverbial fly on the wall to hear what others would talk about us when remembering us. Dawson's portrayal of Torres paying respect was particularly nicely conceived and performed.
Still, none of this is really new material. We've all seen this done more effectively. And the big problem is that the story's conclusion undermines all the actors' attempts to convey a genuine sentiment.
To put it bluntly, the "revelation" that Kathryn's father is really an alien trying to coax Kathryn's consciousness out of her dying (but still slightly alive) body and into his "matrix" is stale, stale, stale. Worse yet, anyone would see it coming about a mile away, because the way the show is structured makes it probably the most predictable episode of Voyager this side of "Basics, Part II." Did I believe for a second that Janeway's father was a real spirit? No, because I just know better. Voyager doesn't believe in ghosts or ghost stories; the writers strive to explain near-death anomalies in "sci-fi" terms. Hence the alien of the week.
Once Janeway began suspecting that her father wasn't really her father, the show may as well have been over, because Cariou and Mulgrew face off in a "fiery" dialog scene that's overstated and overacted. Janeway would need to be a fool not to see through the alien's ruse given how obvious and desperate his persuasion attempts turn. Some subtlety would've been nice, but the ending certainly doesn't supply it. (Janeway's "Go back to hell, coward," fell rather flat, too. It was simply excessive.)
Another big problem is that the entire episode is really just a battle inside Janeway's mind brought on by the alien's influence. This means that nothing in the episode really happened. Everything Harry and B'Elanna said at Janeway's wake; Tuvok's solemn log entry; Kes' hope to find her captain—all imaginary happenings that never took place. The fact that all the characterization in the show is a dream proves quite frustrating.
(Before I get people telling me that "The Visitor" didn't really happen either, let me quickly point out that "Visitor" was based on a time anomaly and not an arbitrary alien-induced figment of imagination. Besides, "Visitor" was about 25 times more moving than "Coda" is, and the real issue here is that there are good ways to use a premise that exists outside conventional reality and bad ways. "Coda" is not an example of the good way.)
Also, in retrospect, what is the point of the time loop motif? A closer look reveals that the idea just doesn't fit in with the rest of the story, so why do it? It apparently serves no purpose beyond a MacGuffin to confuse the audience early on. If the whole episode would've followed this lead into a maze of convoluted surrealism I probably would've enjoyed it much more, but it didn't; it transformed into a by-the-numbers drama with a disappointing ending.
Hey, the show isn't a total loss. Some of the acting is decent stuff. Roxann Dawson's speech during the wake and Robert Beltran's scene when Janeway dies in his arms are notable standouts. Also, some of the chemistry between Janeway and Chakotay in the opening and closing are among the show's best scenes (perhaps because they were among few scenes that actually happened). I'm not saying we need to see an affair between these two characters, but the amiably-portrayed affection is definitely nice.
But if I have to witness the crash of one more shuttle on Voyager, I'll be forced to slay somebody.