"Who Goes There?" is a science fiction novella written by John W. Campbell. It was published under the pen name Don A. Stuart in 1938 in the magazine Astounding Stories. It directly inspired the 1951 movie The Thing from Another World and the 1982 John Carpenter movie The Thing, and indirectly influenced the next few decades of science fiction by inspiring other authors to rip it off. The X-Files, for instance, adapted it twice.The story follows a group of scientific researchers in Antarctica who stumble upon an alien life form. In the novella (and the John Carpenter film) the alien has the ability to assume the identity, memories, and mannerisms of the humans. Which members of the expedition are still human, and which are aliens pretending? As the ice that's keeping them isolated begins to thaw, they'd better figure it out soon, because the fate of humanity is very much at stake.
This novella provides examples of:
Alien Blood: The greatest weakness in the creature's disguise is that its blood, once separated from the body, is a separate organism with its own instinct for self-preservation.
Ape Shall Never Kill Ape: People repeatedly make the mistake of assuming that you can't be a Thing if you attack a Thing.
The Assimilator: It's a little different (and less nightmarish) than the movie version created by John Carpenter. While the thing can absorb people and create multiple copies, the creature is less like a virus and more of highly morphological plasticity. While pieces of its body will act independently of the main body, they cannot infect and devour people from within. Instead this version of the thing seems to envelop and digest organisms to copy them and grown more copies. Still horrific but less so than an enemy that can attack you on a cellular level.
Genre Savvy: Aside from thawing The Thing out in the first place, everyone is extremely rational about the situation, possible consequences, and lines of action. Death by Pragmatism is completely averted.
Garry spoke in a low, bitter voice. "Connant was one of the finest men we had here—and five minutes ago I'd have sworn he was a man. Those damnable things are more than imitation." Garry shuddered and sat back in his bunk.
And thirty seconds later, Garry's blood shrank from the hot platinum wire.
Mysterious Antarctica: The setting for the novella. The Carpenter movie also uses Antarctica, but the 1951 movie uses the North Pole.
No Biochemical Barriers: A Discussed Trope here. Most of them think it's illogical for something from another planet to be compatible enough with humans to eat and/or infect them. They learn the hard way that the universe is always one step beyond logic.
Thirty-Seven Little Murder Victims: The extreme cold outside forces the researchers into close proximity where they can all see each other easier, but the creature can also assimilate them easier.
Paranoia Fuel: Yeah, trapped in the middle of nowhere, stuck in an ice base by storms and cold, with a shapeshifting alien that can eat you and duplicate you while making multiple copies of itself. There's a good chance you won't be getting any sleep tonight while your clutching a weapon glaring at the door.
Phlebotinum du Jour: Since this was written before nuclear power was a practical proposition, electricity and magnetism are the focus of all the high technology. The radios and planes are disabled by breaking their magnets, and the Thing is killed with an overpowered high-tension cattle-prod.
Right Hand Versus Left Hand: The protagonists assume—incorrectly—that you can't be a Thing if you attack a Thing. As it turns out, its imitation is so good that it won't break character if another Thing gets outed, and will attack it just to keep up its own appearance. Once separated, every individual Thing has its own survival as its own priority. That's why the blood test works.
Shock and Awe: the best way of permanently killing The Thing is electricity, high voltage, for as long as it takes.
What Happened to the Mouse?: Benning is a mauve shirt throughout, but generally tags along with barclay and macready, but his final fate isn't revealed. It can be assumed he survived, as he was not mentioned by macready when he lists a few things, and the odds were generally in his favor.