A group of scientific researchers, isolated in Antarctica by the nearly-ended winter, discover an alien spaceship buried in the ice, where it crashed twenty million years before. They try to thaw the inside of the spacecraft with a thermite charge, but end up accidentally destroying it when the ship's magnesium hull is ignited by the charge. However, they do recover the alien pilot from the ancient ice, which the researchers believe was searching for heat when it was frozen. Thawing revives the alien, a being which can assume the shape, memories, and personality of any living thing it devours, while maintaining its original body mass for further reproduction. Unknown to them, the alien immediately kills and then imitates the crew's physicist, a man named Connant; with some 90 pounds of its matter left over it tries to become a sled dog. The crew discovers the dog-Thing and kills it in the process of …show more content…
The researchers try to figure out who may have been replaced by the alien (simply referred to as the Thing), in order to destroy the imitations before they can escape and take over the world. The task is almost impossibly difficult when they realize that the Thing is also telepathic, able to read minds and project thoughts. A sled dog is conditioned by human blood injections (from Copper and Garry) to provide a human-immunity serum test, as in rabbits. The initial test of Connant is inconclusive as they realize that the test animal received both human and alien blood, meaning that either Doctor Copper or expedition Commander Garry is actually an alien. Assistant commander McReady takes over and deduces that all the other animals at the station, save the test dog, have already become imitations; all are killed by electrocution and their corpses