A decent, ordinary life jeopardized by a catastrophically extraordinary event: this is the story, mythic in its outline and substance, that Judy Troy--author of two New York Times Notable Books and Whiting award winner--tells in From the Black Hills.        In Wheatley, South Dakota, during the summer before Mike Newlin is to begin college, his father, an insurance salesman, shoots and kills the young woman who works for him as his receptionist. He disappears, and Mike is left behind in shock and grief. With his future suddenly obscured, Mike finds himself nearly overwhelmed by his present circumstances--not only the emotional damage inflicted by his father's awful crime but also his mother's dismay, the insinuating methods of a criminal investigator named Tom DeWitt, his girlfriend's anxieties, and his longing for an older woman who lives nearby--and the question of whether he will ever see his father again and what will happen if he does.      As imposing as the landscape that forms its setting, From the Black Hills conveys with compassionate power the drama of a young man who must try to overcome his father's dark legacy.