The Man Trap

The central idea of this story was anticipated by an episode in A E van Vogt's "The Voyage of the Space Beagle" (itself an anticipation of "Star Trek"). A creature that resembles a mountain lion with tentacles sucks the "id" (potassium) from its victims' bodies. (There's no explanation of where other essential nutrients come from.)

I understand why some fans don't much care for this episode. Though not intended as such, it resembles the "monster of the week" sort of story ABC insisted on for "The Outer Limits". As for the creature's failure to ask Kirk for a metric ton or two of salt -- Ryder urgently requested salt, but Kirk failed to provide it.

I like it for a number of reasons, principally that it's cool and low-key (in contrast to the noisier theatrics of almost every episode that followed). The photography is grand, making effective use of pools of light against darker backgrounds. (This would soon disappear.) There's almost no music, with sound effects creating an eerie atmosphere. From a strictly "aesthetic" perspective, "The Man Trap" is arguably the best of all the Classic episodes.