Infinite Intruder
by Alan E. Nourse
Since the 4-day atomic war of 2078, Roger Strang has been working on the Barrier Project
to build an electronic barrier against missiles, but now someone is trying to kill his
12-year-old son with attacks that seemingly succeed but don’t, while any records of his
own background have been erased, as if he had never even lived, at least not in the 21st
century. As a bonus, the story also has a grandfather paradox.
The theory said that a man returning through time could alter the social and
technological trends of the people and times to which he returned, in order to change
history that was already past.
“Infinite Intruder” by Alan E. Nourse, in Space
Science Fiction, July 1953.