"No one knows Margo's real name. Her colleagues and patrons at a small-town public library only know her middle-aged normalcy, congeniality, and charm. They have no reason to suspect that she is, in fact, a former nurse with a trail of countless premature deaths in her wake. She has turned a new page, so to speak, and the library is her sanctuary, a place to quell old urges. That is, at least, until Patricia, a recent graduate and failed novelist,...