"I'm working on the greatest mystery ever," was the last thing noted mystery novelist Mercedes Livingston said to seven-year-old Chris Matheson before walking out of Hill House Hotel never to be seen again. For decades, the writer's fate remained a puzzling mystery until an autographed novel and a letter put a grown-up Chris Matheson on the trail of a cunning killer. With the help of a team of fellow retired law enforcement officers, each a...