"Captain, it doesn't even look real."
The yeoman-of-the-week has put her finger right on the episode's main problem: plausibility. As monster stories go, this is one of the weakest they ever told. After the previous week's subtle character-based drama, this is all cheesy monster and cheap theatrics.
Jim Ruggs, the on-set special effects man, has a real chance to shine. On the one hand, he does (the creatures breathing, dripping and dissolving as they are killed). On the other hand, he does not (the creatures flying around and landing on Spock). He's also at the mercy of the creature's creator (uncredited) who has given him an obviously rubbery blob painted with spots.
Perhaps the physical manifestation of the menace would be less offensive if the character problems were a little more carefully considered. It seems utterly unnecessary to kill off Kirk's brother in such a cheap situation. (Picard's brother, alas, suffered the same fate.) The drama is so minimal that Shatner has almost nothing to work with, and the whole thing (including the nephew) is long-forgotten by the end of the episode. At least Joan Swift provides a plausibly anguished turn as widow/victim before that whole angle fades away.
Similarly, the problem is solved in a classic quick fix moment when Kirk turns on some gizmo and remembers that stars give off light -- a fact which his senior staff has failed to remember. They whip up some satellites and the creatures die. Once again, our crew has solved a problem which had been raging for centuries in about 50 minutes.
Not that they shouldn't be capable of such things -- after all, saving the galaxy is the mission they trained for -- but it's a cheat to give them such a gigantic problem and then have the solution arrived at by luck, guesswork, and sloppy science (in which a character is needlessly maimed). The characters are changed, but the changes are shallow, not motivated by anything lasting, and will be gone by next week.
This leads to the episode's capper: Spock's positively soap-opera-esque temporary blindness. While the moment his blindness is revealed and the Kirk-McCoy interaction which follows packs some intensity, the unraveling of the problem simultaneously unravels everything which might have been of value for the characters. To top it off, it's followed by a couple of lame (and derivative, and repetitive) jokes.
The first season ends with a whine -- from the creatures and the viewers. Had the show itself ended here, I doubt we'd be talking about it today.
Rating: Bottom (6)