the enterprise approach a denova and be surprise that they can not hail anyone the planet just seem dead . so and they beam down and find most of the people either dead or insane with an overwhelming desire to kill . it turn out that there be alien creature who look like plastic barf you buy from novelty store and it responsible . this fly barf and once it hit you and take over your mind and use pain to motivate you to do evil . kirk brother and his family be among the victim and this aspect of the show do not seem all that convince . a short time later and spock be hit by this fly barf and he be infect . so and they use spock to test out various way to kill the creature and everyone be save . oddly and you do wonder why the enterprise could figure all this out so quickly and yet the folk on the planet be totally screw . this be an episode that seem to be air less often than average perhaps because it be a pretty weak one with a lot of plot problem . the creature be pretty cheesy and the plot not terribly exciting and but probably the big shortcoming of the show be the gimmicky way they resolve the end of the film when spock be blind when try to kill off the space barf that have infest him . have it all just work out fine after all seem very contrived . for devoted fan and this be worth see but for everyone else and it quite skip able .