In the "Star Trek: The Next Generation" episode "Identity Crisis", Geordi La Forge (LeVar Burton) discovers from an old friend named Lieutenant Commander Susanna Leijten (Maryann Plunkett) that they are the only two people still alive and accounted for from a mysterious away mission on the planet Tarchannen III, conducted years before. The other members of the team have all mysteriously fled to Tarchannen III -- sometimes stealing shuttlecrafts to do so -- and vanished without a trace. It won't be long before Leijten begins exhibiting strange, nervous symptoms of an unknown disease, causing her to become fearful and twitchy. She, too, it seems, is being irresistibly drawn back to Tarchannan III. Is Geordi next? Not to spoil anything, but yes he is.

It's eventually revealed that an undetectable spore on Tarchannen III infected the members of Geordi's old away mission, causing them to mutate. It seems the spores are...