Barry N. Malzberg 
Scop [EPUB ebook] 

Bitterly, Bitterly, Scop is a failure!Scop is doing his job . . .He has spoken to President Kennedy, warning him to leave Dallas immediately . . . spoken to Zapruder, asking him not to take pictures . . . pleaded with Elaine Kozciouskos, begging her only to scream, has even fornicated with her — part of the job. In spite of the pain, he has witnessed, on location, the last minutes of Jack Kennedy, King, Malcolm, Robert Kennedy — all for the fate of mankind.But bitterly, bitterly, he knows he is a failure. Scop is trying to alter, has merely reinforced the future . . .