The Enterprise approach a Denova and are surprised that they can't hail anyone--the planet just seems dead. So, they beam down and find most of the people either dead or insane--with an overwhelming desire to kill. It turns out that there are alien creatures who look like plastic barf you buy from novelty stores and it's responsible. This flying barf, once it hits you, takes over your mind and uses pain to motivate you to do evil. Kirk's brother and his family are among the victims and this aspect of the show didn't seem all that convincing. A short time later, Spock is hit by this flying barf and he is infected! So, they use Spock to test out various ways to kill the creatures and everyone is saved. Oddly, you do wonder why the Enterprise could figure all this out so quickly and yet the folks on the planet were totally screwed! <br /><br />This is an episode that seems to be aired less often than average--perhaps because it is a pretty weak one with a lot of plot problems. The creatures were pretty cheesy and the plot not terribly exciting, but probably the biggest shortcoming of the show is the gimmicky way they resolved the ending of the film when Spock was blinded when trying to kill off the space barf that had infested him. Having it all just work out fine after all seemed very contrived. For devoted fans, this is worth seeing but for everyone else, it's quite skip-able.