These twelve stories are generally good with one stand-out in Wilma Shore's A Bulletin from the Trustees where a man is brought back from the future and knows Just about as much of what's going on in his world as our man on the street--knows his ballgames but not his congressman, let alone the material of his suit. There's a pretty good variation on using the past to change the present in William Tenn's Brooklyn Project while Alfred Bester proves that you can't alter it with The Men Who Murdered Mohammed.