Plot
In the winter of 1982, members of the Norwegian research station "Thule" discover an alien spacecraft and a nearby alien body buried in the Antarctic ice. Dr. Sander Halvorson and his assistant Adam Finch recruit American paleontologist Kate Lloyd to investigate. Together with pilots Sam Carter, Derek Jameson, and crewman Griggs, they fly to Thule Station and meet station chief Edvard Wolner, along with his team of Juliette, Karl, Jonas, Olav, Henrik, Colin, Peder, Lars, and Lars' dog.
The body, encased in a block of ice, is transported to Thule Station. While the team celebrates their historic find, Jameson witnesses the Thing burst from the ice block. The team splits up to search for the alien and find Lars' dog dead. The alien drags Henrik into itself, spattering blood on Olav. The group kills the alien by igniting spilled fuel beneath it. An autopsy reveals that the alien's cells were copying Henrik's. Olav falls ill.
As Carter, Jameson, and Griggs are taking off in the helicopter to take Olav to a medical facility, Griggs transforms into a Thing and attacks Olav, causing the helicopter to crash in the mountains. Kate discovers dental fillings in a bloodied shower and alerts the team that the alien can assimilate and imitate its victims to hide among them. Edvard orders the team to drive to the closest base; however, Juliette and Kate want to prevent anyone from leaving. After going with Kate to get the keys to the vehicles, Juliette transforms and attempts to kill her. Kate escapes and the Juliette-Thing kills Karl. Lars kills the Juliette-Thing with a flamethrower and the team resolves to quarantine themselves until the threat is eliminated.
That night, Carter and Jameson stagger back from the crash. Suspected of being infected, they are kept in isolation. As the alien does not assimilate and imitate inorganic material (as Kate realized from the discarded dental fillings), Kate proposes everyone to be checked for dental fillings. The test clears all but Sander, Edvard, Adam, and Colin, as they have no metallic fillings.
Lars is abducted while going to fetch Carter and Jameson for testing. Carter and Jameson break into the main building, shooting Peder dead and puncturing his flamethrower tank, causing an explosion that knocks Edvard unconscious. When brought to the main room, Edvard violently transforms into the Thing, infects Jonas, kills Jameson, then assimilates Adam, becoming a two-headed thing. Kate burns Jonas and Jameson before they can fully transform, then she and Carter burn the Edvard/Adams-Thing before pursuing Sander, who had also been assimilated.
The Sander-Thing drives in a snowcat to the spaceship. The spacecraft suddenly activates, shifting and separating Kate and Carter, with Kate falling into the ship and Carter proceeding through the main hatch. Kate encounters the monstrous Sander-Thing and kills it with a grenade, which shuts down the ship's engines. Kate finds Carter and notices that he is missing his earring; Carter reaches for the wrong ear, confirming to her that he is the Thing in disguise. Kate burns the Carter-Thing, preventing its escape. Kate enters a second snowcat and prepares to drive to the Soviet base 50 miles away.
The next morning, Thule's helicopter and pilot Matias returns to the ruined station. Matias finds the burned remains of the two-headed Adams-Thing. Colin's corpse sits in the radio comms room, his wrists slit and a straight razor held in his hand. Lars, having been hiding in the building where Jameson and Carter attacked him, demands at gunpoint that Matias show his teeth. Lars' dog, thought dead, emerges and runs away. Realizing that the dog is a Thing, Lars orders Matias to give chase in the helicopter.