It's the first week of winter in 1982. An American Research Base is greeted by an alien force, that can assimilate anything it touches. It's up to the members to stay alive, and be sure of who is human, and who has become one of the Things.
After a space merchant vessel perceives an unknown transmission as distress call, their landing on the source planet finds one of the crew attacked by a mysterious lifeform. Continuing their journey back to Earth with the attacked crew having recovered and the critter deceased, they soon realize that its life cycle has merely begun.