The Devil in the Dark
Workers on a mining colony are slaughtered by a rock-like creature lurking in the deep tunnels. But is it something more than a vicious animal? Spock believes so, but Kirk is on the war path.
Both Nimoy and Shatner always cite this as their favorite episode, with its unobjectionable theme of overcoming fear and misunderstanding through communication. Unfortunately, they're communicating with what is possibly the silliest looking space creature ever. I figure it was intended to look like a lava, but appears more like a pizza-stained shag rug. (Note the fringes.) A silicon-based creature is brilliant in theory, but the execution? Sadly not. Still, we must commend our actors for their meaningful interactions with the bad prop, from Spock's painful mind meld to Bones's bricklaying. The initial cave explorations scenes, with redshirts and miners getting fried left and right, seem extraneous, but lead to better things. Kirk and Spock's role reversals as one wants to kill the Horta while the other begs mercy is most interesting. The eggs are kind of obvious from the beginning, but not the symbiotic relationship possible between the miners and Horta. A happy ending.
Spock Saves the Day: Spock pleas that the Horta be spared, tries to rescue Kirk from it, communicates with it, and befriends it.
Oops: The "PAIN!" line is way over the top.
Developments: Mind meld number two starts off rough, but Spock eventually gains full empathy for the creature. He doesn't need to touch it to sense its pain, and the Horta learns a few words at this distance. Once in full contact, the Horta speaks through Spock, as his subjects often do. It's worth noting that the only moment Spock wants to kill it is when Jim's in imminent danger. But some of the Vulcan's compassion and reasoning rub off on the captain, and they've decided not going to kill, today.