When they published the title story of this collection in April 1947, "Astounding Science Fiction" said, "To upset the stable, mighty stream of time would probably take an enormous concentration of energy. And it's not to be expected that a man would get a second chance at life. But an atomic might accomplish both --" John W. Campbell was a man who really knew what makes SF the appealing thing it is; it's no wonder that he published the story. Also included in this volume are "The Mercenaries" ("Astounding Science Fiction, " March, 1950), "He Walked Around the Horses" ("Astounding Science Fiction, " April 1948), "The Return" ("Astounding Science Fiction, " January, 1954 -- a collaboration with John J. McGuire), and "Temple Trouble" ("Astounding Science Fiction, " April, 1951).