Where are you now?

Ten years ago, twenty-one-year-old Columbia University senior Charles MacKenzie Jr. ("Mack") walked out of his Manhattan apartment without a word with his roommates and disappeared. He calls his mother once a year, on Mother's Day, but refuse to answer her frantic questions. This year when he calls, Mack's sister Carolyn, now twenty-six, announces her intention to trace him down, no matter what it takes. Ignoring a cryptic warning note and the angry protests of her mother, Carolyn swifly plunges