"Operation -- Annihilate!"
Nicholas Meyer is so fond of talking about how "Art thrives on restriction," which is not entirely baseless (sometimes, though, you really need good resources to bring the best to the screen). The location shoot looks really great. Even 50 years later, it's interesting and visually striking and, I suppose, the facility was "paid" with free publicity, at the time. So, there's $aving$, there, that work for this episode. The alien creatures are absolutely brilliant. They're like a buck-and-a-half's worth of plastic, but it's brilliant, how effective they - still - are at getting the story told. And what they're meant to represent is an over-the-top concept that I think really works, here.
The threat is dealt with locally, even globally and the stakes are Galactic! This is a very densely layered episode with so much on offer that anyone, at all, is going to like it. I mean, even on Down-to-Earth terms, Captain Kirk's family is relevant to the story. And we even get to learn a thing or two about Mister Spock. For 1960's television, this episode is surprisingly thoughtful and intelligently written. Whilst not, exactly, my most favourite TOS offering, it's certainly one of them and I qualify it as one of the best, overall.
