At a military base in Anchorage, Alaska, Air Force general Fogarty orders Captain Patrick Hendry and his crew to fly to a scientific research station at the North Pole to help Dr. Arthur Carrington investigate the landing of an unidentified object. During the flight, Pat receives a radio call from the station, alerting him to a recent "disturbance" in the area, which has been causing inaccurate instrument readings. Shortly after the military men arrive at the station, Carrington tells Pat about the landing of a large, mysterious object. He then shows Pat photographic images taken by a telescopic camera, which indicate that the object flew upwards before landing and therefore could not be a meteor. Pat, his men, reporter Ned "Scotty" Scott, who has accompanied them from Anchorage in search of a story, and a group of scientists led by Carrington fly to the object's estimated location. Protruding up from an area of thin, radioactive ice, they spot an air foil and determine that it is attached to a circular craft, which they presume to be extraterrestrial. To free the craft, a thermite bomb is planted, but the explosion triggers another, bigger blast that destroys the object. Just as Scotty starts to bemoan the loss of his story, the team's Geiger counter alerts them to the presence of a large manlike creature buried nearby. To preserve the creature, the men cut it out of the ice in a block and fly the block to the station. There, Pat defies Carrington and orders that the creature not be thawed and that the men take turns guarding it. Pat then tries to contact Fogarty for instructions, but learns that a blizzard has disrupted communications. Later, while guarding the extraterrestrial, Corp. Barnes becomes unnerved and places an electric blanket over the ice, unaware that the blanket is turned on. Soon, enough ice has melted to free the creature, who suddenly comes to life and threatens Barnes. Terrified, Barnes shoots at the creature, but it flees the storeroom and stumbles into the snow. Barnes and the others then watch in disbelief as the creature fights with several sled dogs, killing two before running off. Near one slain dog, the men find a severed arm and examine it in the laboratory. Carrington and the other scientists conclude that the extraterrestrial is made of vegetable matter but is highly intelligent. Then, when the severed hand begins to flex, the scientists realize that it is feeding off the dog's blood on its fingertips. Although Carrington demands that the creature be studied, not hurt, Pat and his ax-wielding men are determined to kill it. Once alone with his fellow scientists in the station's greenhouse, Carrington reveals that the creature broke the outside door lock, entered and then left after repairing the lock. Noticing some sap on a storage bin, the scientists open the bin, and a dead, bloodless dog falls out. Later, as the military men again attempt to reach Fogarty, Dr. Stern, one of the scientists, stumbles into the room and announces that the "thing" attacked him and two others in the greenhouse, leaving the other two hanging upside down with their throats slit. When Pat and his men go to investigate, the creature, its severed arm restored, surprises them at the greenhouse's inside door, but they manage to throw up a barricade before it can get out. In the nursery, Carrington then tells the other researchers that the alien planted a seed in the greenhouse and was feeding it with the dripping blood of his human victims. Carrington also reveals that he planted an alien seed found in the severed arm, and shows them how it multiplied at a spectacular rate after being fed blood plasma. Soon after, Pat questions Carrington's secretary, Nikki Nicholson, with whom he enjoys a serious flirtation, about the disappearance of the blood plasma supply. She reveals Carrington's activities, and Pat confronts the scientist. Although he dismisses Carrington's plea that the new life form must be researched, Pat is overruled by Fogarty, whose order to preserve the alien finally comes through on the radio. Later, however, as the temperature becomes dangerously cold for the outside guards, the military men realize they must kill the creature to save themselves. Taking Nikki's suggestion, they set a trap using kerosene, but the alien is only slowed by the fire. The military men then decide to electrocute the alien, but as they are devising the new trap, Nikki discovers that the creature is shutting off the heat in the complex. For protection, the group moves to the generator room and quickly begins building the trap. As the extraterrestrial lumbers toward the generator room, lured by the smell of flesh, Carrington tries to derail the men's efforts and even attempts to talk to the creature. The alien knocks Carrington to the floor, then unwittingly walks into the trap. Shocked with powerful electrical bolts, the creature slowly disintegrates. Later, as Nikki and Pat contemplate marriage, Scotty is able finally to file his story over the radio and warns his audience to "keep watching the skies!"