Kirk and the crew are visiting a federation mining colony on a remote planet rich in mineral resources. The Devil in the Dark is the Horta, a very unusual silicon based life-form which tunnels through solid rock. The Horta has been killing miners and, it is decided, must be destroyed. But how? <br /><br />It is hard to continue this review without writing a spoiler, so instead I simply concentrate on the technical aspects of the episode and touch on its themes. The special effects are OK, but many of the scenes with the Horta look a little absurd. The acting is fairly average for TOS. Some of the miners are a little awkward. Nimoy has the most difficult role of all in Devil in the Dark, and he pulls it off well. <br /><br />Why is this still a favorite of mine?<br /><br />Devil in the Dark is really an anthropological and ecological morality play disguised as an adventure. More than many episodes of this great TV series, it brings home the importance of maintaining an open mind and at least some degree of empathy toward others. Plus, it involves one of the most interesting, if not probable, plot twists in the original series. <br /><br />Enjoy!