Books like Where are you now? by Mary Higgins Clark

Ten years ago, twenty-one-year-old Columbia University senior Charles MacKenzie Jr. ("Mack") walked out of his Manhattan apartment without a word to his roommates and disappeared. He calls his mother once a year, on Mother's Day, but refuses to answer her frantic questions. This year when he calls, Mack's sister Carolyn, now twenty-six, announces her intention to track him down, no matter what it takes. Ignoring a cryptic warning note and the angry protests of her mother, Carolyn swiftly plunges into a world of unexpected danger and unanswered questions. What do Mack's old roommates—a charismatic club owner and a wealthy real estate tycoon—know about his disappearance? Can the police possibly believe that Mack is a shadowy predator—or even a murderer? Carolyn's passionate search for the truth leads her into a deadly confrontation with someone close to her whose secret he cannot allow her to reveal.

First publish date: 2008