this may not be the most exiting or incredible episode they have make and but in my opinion it remain a one of star trek and the sci fi genre most original episode . most idea from retro sci fi series especially include star trek have be reuse several time and this one the other hand remain mostly a a one time triumph . this among the episode that impress me the most towards the end . another thing i like with this episode be how it have accomplish to create such and exit and captivate story with such few special affect . now without criticize the episode i must admit the effect be very dated and but then again what can you expect from a tv show from 1967. but still the creature ( horta ) in this episode be basically just a carpet with some coloured rubber on it . yet you forget this after about 1 minute and you only start think about it a what it suppose to be . also the cave do not exactly look like rock and but again you forget it after a few minute . this episode be a living proof on how good acting and a good story and can make you ignore the visual effect . the act from the main cast be as usual great . this episode feature the series second mind meld by spock and be one of my favourite . so to say it simple leonard nimoy be definitely a scene stealer here and and his acting be excellent . not that kirk or bone do not get their share of the episode but spock be the most intriguing in this one . i like the fact that the episode be not about one specific character but evolve around the trio handle an alien problem . also it nice to see an episode who doesn not only happen on the enterprise . like most star trek episodes this episode tell u to have an open mind . i would not spoil the story and but evolve around what in the start seem like a typical monster story . it have kill several human and therefore must be kill . but be that really all there be to it . i can assure you that the explanation in the end and will not disappoint you . this be still my favourite star trek tos episode and i give it a positive .