I sympathized with the plight of the first man, Schmitter, we see killed in this episode. He reminded me of the trepidation associated with being a lone security guard at night somewhere - the type of work I did briefly about 20 years ago. Of course, I was never in danger of being burned to a crisp, as the colony chief (Lynch) is fond of describing. The monster in the dark here, murdering members of a deep mining colony, creates a scary impression in the first act. We don't really see it in the early scenes and, as many of us realize, the best monsters are sometimes left to the imagination. 'Big and shaggy' is one voiced description, but it actually turns out to resemble a big, lumpy pepperoni pizza, skittering along the ground like a silicon centipede - a limitation of the show's budget, unfortunately. This also shows in the latest matte painting, famous to Trek fans, the only way to convey a long shot of the mining operations.<br /><br />But, the whole theme of this episode is about what's on the inside, rather than outward appearances, anyway. Sure, this Horta, a newly-discovered silicon-based life-form, looks like a mindless monster at first glance. Thanks to Spock's telepathic ability (probably the best use of a Vulcan mind meld for plot purposes), we learn it's a highly intelligent, even sophisticated creature. Besides Spock's instrumental use of his talent, McCoy gets to supersede his usual medical routine - healing a creature resembling rocks or asbestos. He also gets to utter one of his most famous lines, "I'm a doctor, not a bricklayer!" I found it very true-to-life in his scene where he exults in his success, though he's unable to get Kirk to share in his enthusiasm - Kirk's too busy organizing results. The episode throws unexpected turns in character & motivation at the audience as the story progresses; Spock champions the need to possibly preserve this discovered life as Kirk takes his usual stand on preventing the deaths of any red-shirts (no half measures, as in "The Man Trap"). But later, it's Kirk who, for some reason, holds back on firing a killing blast, as if the heat of the hunt had worn off and he'd had time to reflect on Spock's point (I believe it was during this episode's filming that Shatner learned his father had died). Uncharacteristic for most of the first season, this has a happy ending. The conflict stems from the needs of basic capitalism, such as meeting standard quotas, versus protecting the natural environment and its inhabitants - a space age version of protecting owls from the tractors of modern advancement. Somehow, despite many killings and a sense that everything could go to hell at any moment with one raised phaser, Kirk and Spock manage to broker an agreement which satisfies everyone. I guess people and silicates are more reasonable in the 23rd century.