Episode Description: Beware, spoilers! To read - hover over the text.
In Alaska killed a geological expedition, which bore a layer of permafrost. In the investigation Scully go with Mulder, geologist, physician and toxicologist. Survivors on the station the dog bit the pilot and it got infected. The reason - small microorganisms that had lain 200 thousand years under the ice. The cure is to infect the infected. The parasite does not make a relative and they both die.