After Sgt. Mason begins an experiment to determine the effects of isolation on the human body by being locked in a capsule deep below the earth's surface. There, he opens the capsule only to be attacked by giant Insect creatures looking to experiment on him. After fleeing them, he manages to find sanctuary in the capsule and requests return to the surface. There, his superiors decide his story is the work of hallucinations brought on by the isolation. They do not notice a janitor sweeping up an insect hair over a foot long.