Basic Outline:

Players(us) are plunged into a post-apocalyptic world on a planet called Circa Minor. There was a laboratory incident that released a deadly virus into the atmosphere and the planet is mostly uninhabitable. For the small areas that are still safe to live in, starving creatures and dangers lurk. The few people who survived are forced to live in the deepest caves with no exposure to the light of day- even though the surface is smothered by a thick dark smog and stinks of decay and death. Perhaps resources are still out there, but one would have to go to the surface to get them...