||I've always liked this one, for two reasons. Firstly, they tried to show something genuinely alien (even if it was just a man crawling around under a blanket). Secondly, the monster gets a chance to redeem itself, almost making us look like monsters in the process. It's not often we get to see an alien invasion from the point of view of the aliens. Essentially, that's what we have here, and it takes a different perspective to understand what is really going on. Like a lot of TOS, it's a fairly simple story, but it works. There did not seem to be any outstanding performances, but it was still fairly convincing. Also, in the days before SIMs beacons, we had an astonishingly well-lit mine (presumably to avoid Kirk having to carry a flashlight with him). A Silicon-based creature might just about work biologically, but I'm not sure about that. Overall, a decent episode, with a very good message.