From the Publisher's Website:
An American scientific expedition to the frozen wastes of the Antarctic is suddenly disrupted by the arrival of a husky, pursued by two Norwegians in a helicopter. The Norwegians fire indiscriminately at the dog. The team members defend themselves and shoot back, killing the Norwegians.
It doesn't take long before the Thing (in dog form) attacks the team. One by one, they are picked off and replaced by Thing duplicates.
As the expedition explores the Norwegian camp, the history of the Thing comes together. Centuries ago - an alien spaceship had crash-landed in the Antarctic. The pilot was thrown clear and eventually froze in the ice. But the Norwegians uncovered it. And then they thawed it out.
The Thing is a cellular colony that imitates other beings. It has the ability to alter its own cell structure to that of a consumed organism, and can thus imitate a victim almost perfectly.
If the Thing were to ever reach civilization, it could replicate so quickly that in a matter of days, it would duplicate every living being on Earth. It's up to the PCs to stop it...before the Thing stops them.
The Thing: Who Goes There? is a supplement for D20 Modern that contains five advanced classes, lots of equipment, rules for fear and trust, hazards, and seven Thing variants.