As a park ranger on the National Park Service's law enforcement team, Andrea Lankford led search and rescue missions in some of the most beautiful (and dangerous) landscapes in America, from Yosemite and Zion to the Grand Canyon. But though she had the official support of the agency, Andrea found herself increasingly frustrated with the service's bureaucratic idiosyncrasies, and after twelve years, she finally left the force, haunted by her own failure to find a lost hiker in 1995. Two decades later, however, she stumbles across a mystery that pulls her right back where she left off: three young men have vanished from the Pacific Crest Trail, the 2,650-mile trek made famous by Cheryl Strayed, and no one has been able to find them. It's bugging the hell out of her.Andrea's concern leads her to a wild environment she didn't have to traverse when she last searched for the lost: missing person Facebook groups. Andrea launches an investigation, joining forces with an eclectic team of amateurs who are determined to solve the cases by land and by screen: a mother of the missing, a retired pharmacy manager, and a mapmaker who monitors terrorist activity for the government. Together, they track the activities of kidnappers and murderers, investigate a cult, rescue a psychic in peril, cross paths with an unconventional scientist, and reunite an international fugitive with his family.Searching for the missing is a brutal psychological and physical test with the highest possible stakes, and it takes its toll on each of them. And the insidious nature of the internet wreaks havoc on their investigation, with obsessive ''fans'' of missing person pages offering fabricated clues, financial requests, and, most damaging of