On the night of her high school graduation, Richelle Bach's father gives her and her identical twin sister, Michelle, matching opal necklaces. "These opals look identical," he tells them, "but the fire inside each is completely unique--just like the two of you." Indeed, the two sisters couldn't be more different, and their paths diverge as they embark on adulthood. Years pass, until--at their father's behest--they both come home for Christmas. What...