The friendship between Mary and Nix had endured since childhood, a seemingly unbreakable bond, until the mid-1980s, when the two young women embarked on a summer vacation in Greece. It was a trip initiated by Nix, who had just learned that Mary had been diagnosed with a disease that would cut her life short and who was determined that it be the vacation of a lifetime. But by the time their visit to Greece was over, Nix had withdrawn from their friendship,...