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.

Variants

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  1. “Infinite Intruder” by Alan E. Nourse, in Space Science Fiction, July 1953.
    2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Alan E. Nourse