The Enterprise(TOS) checking on CSI scientists
Is this one familiar to anybody? Star Trek TOS/CSI crossover. The Enterprise comes to a distant planet to check up on a team of scientists who have been there for quite a while, a year of more with no contact. Everything seems okay and Grissom and team see fine, but Spock seems to think that they are hiding something. Some one is murdered and the Enterprise has to stay and solve the crime. Grissom and several of his team are vampires who like the planet and don't want to leave because it's mostly in the dark.