From firstname.lastname@example.org@21:1/5 to All on Sun Oct 16 12:49:45 2016
Kirk, McCoy, and a crewman named Darnell beam down to a planet (M-113) to visit Robert and Nancy Crater and give them medical exams.
Great moments: Nancy looking like a youngish woman with dark hair to her former boyfriend McCoy, an older woman with dark hair to Kirk, and a blonde to Darnell. Soon, Darnell is panting after Nancy.
Darnell turning up dead with blotches all over his face.
Spock scolding Uhuru over a frequency error, and Uhuru joking that if she hears the word "frequency" one more time, she will get sick.
Darnell died from a sudden loss of salt. Meanwhile, the Craters are asking for salt. This makes Kirk suspicious.
Soon, two more crewmen are dead from salt deprivation, then Nancy assumes the form of one of them to infiltrate the Enterprise. Nancy isn't Nancy. She's a salt vampire who had replaced the real Nancy after killing her.
Robert Crater finally explains that the creature (salt vampire) that has been preying on Enterprise crewmembers and emulating them is the last of its kind. The salt vampires have run out of salt, and there is only one left. Robert compares the salt
vampire situation to the extinction of the buffalo. He doesn't want to kill the last member of an intelligent species. Kirk points out one difference: The salt vampire has been killing people.
It seems to me that killing the salt vampire is totally unnecessary. Just keep it fed with salt (as suggested by Robert Crater and the salt vampire in McCoy form), and its harmless. Why don't Kirk and Spock seem to take that option seriously?