the very first episode of the original trek series to air and though this be the 6th one film . the exec want to start thing with a amonster of the week mentality and but though the creature in this one be responsible for a number of crew death and it more to be pity than revile by the end of the episode . it possess startle chameleon power and couple with hypnotism and telepathic ability and enable it to fool all the cast member during the story a it imitate several of them . unfortunately and it crave salt and which it need to survive and and human body fill the need very well . this be an example of sheer incompatibility between two race and which an angry captain kirk instinctively realize in the 3rd act he know it either his crew or the creature there can be no half measure . we learn how intensely kirk feel when he lose a crewman check out the first killing here and he have to go thru it a few more time in this episode . the enterprise be on a routine check up of 2 archaeologist on a planet with the ruin of an extinct civilization but not all the inhabitant be extinct and a it turn out while there one left . the storyline contain mystery and a chilling revelation . but and much of this episode emphasize the routine represent we never find out anything more about the dead civilization it probably one of many the federation find and explores while ship and crew routine be view during the creature stalking and notably yeoman rand and sulu while there a casual banter between kirk and mccoy which we all come to appreciate and look forward to in the next 3 year . overall and this episode show that future life and while with obvious difference in technology and will be largely the same for u human . if there a theme in this episode and it have to do with the inevitable extinction of a specie and such a the american buffalo and a if it a rule of the universe . we can express sorrow for such a loss a part of the human equation and but and in the end and there nothing we can do about it . however and the reason this episode probably gain some loyal follower of the trek franchise right of the bat be probably not the monster . no and it must have be that easy interplay among the crew and especially the central trio yes and include spock and who right away start insist in this episode how he immune to emotion but obviously enjoy a friendship with kirk ( uhura even spell this out ) . and the human equation be delineate in mccoy story in this one represent he reunite with his old girlfriend and so he charmingly nervous a all hell and but in quick order and find out she be dead and her imitator must be kill and even though she the last of her kind . not only be this a personal tragedy for him and but he also responsible for seal the coffin on an entire specie . the anguished look on his face towards the end be what make this a memorable entry in the trek mythos .