Note: The original serial was expanded for publication as a novel per the 1963 Doubleday edition which has "A shorter version of this work appeared in ANALOG Science Fact—Science Fiction".

Synopsis: The world was gripped in terror when the Nipe, a lethal, alien fighting machine, crashlanded on Earth from outer space and began a nightmarish rampage of slaughter and destruction. Unable to stop the deadly, intelligent creature, scientists quickly developed a plan to turn an ordinary Earthman into a super-human with powers enough to conquer the monster. As the man chosen for the dangerous mission, Bart Stanton was not sure he wanted to give up his humanity. The Nipe seized the Earth's most vital defense secrets and Bart felt he had no choice but to go through with the plan. Then the Nipe mysteriously disappeared - and the only man who could locate the thing was also the only man who could destroy Bart. The world tottered as the three came face to face.. (from the back cover of the Leisure Books paperback edition)