Major Dan Keller works for NORAD, at the computer control section. There he programs complex machinery that watches the skies, constantly. The aliens need a window to bring in a great many saucers, so that they may establish a base on a remote island. To do that, they place one of their own as Dan Keller's new wife Laurie. She is equipped to hypnotize Dan into replacing a crucial programming tape with one the aliens have forged - one that will instruct the systems to ignore certain things they see. Written by
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A physician reports the death of a woman. Two hours later, her husband, a NORAD Major, reports her very much alive. The news accounts attracted no particular attention. But David Vincent knew that an alien, unconscious without pulse or heartbeat, might easily be mistaken for dead, even by a doctor. So he arranged to visit NORAD's Combat Operation's Center, 1,400 feet below Cheyenne Mountain and a natural target for the Invaders.