As a park ranger with the National Park Service's law enforcement team, Andrea Lankford led search and rescue missions in some of the most beautiful (and dangerous) landscapes across America, from Yosemite to the Grand Canyon. But though she had the support of the agency, Andrea grew frustrated with the service's bureaucratic idiosyncrasies, and left the force after twelve years. 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's , and no one has been able to find them. It’s bugging the hell out of her.   Andrea’s concern soon leads her to a wild environment unlike any she’s ever encountered: 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 stakes, but eventually their hardships begin to bear strange fruits—ones that lead them to places and people they never saw coming.   Beautifully written, heartfelt, and at times harrowing, paints a vivid picture of hiker culture and its complicated relationship with the ever-expanding online realm, all while exploring the power and limits of determination, generosity, and hope. It also offers a deep awe of the natural world, even as it unearths just how vast and treacherous it can be.    On the , you may not find what you are looking for, but you will certainly find more than you seek. ** THE INSTANT NEW YORK TIMES BESTSELLER **