Eternity's Handmaiden — R. Peter Ubtrent

Alexis Locke gave the first forty-five years of her life to an agency that never gave a second thought to putting her in harm's way. After fifteen years of voluntarily retirement and seclusion, she is forced to investigate the seemingly accidental deaths of five unrelated scientists, one of whom turns out to be the son she had to give up at birth. Following the clues that lead her from the mega-biotech companies in Kasakhstan to the orbiting O'Neill Colonies, Alexis quickly learns that she is being set up, that her death is wanted by many and that the deaths she's investigating have a far bigger connection that anyone ever thought possible, eventually forcing her to question her own existence and purpose. And with that questioning, Alexis soon sees that there is a plan as work handed down from the future from which she can not escape.