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.

Fans of true crime shows like CSI, NCIS, Criminal Minds, and Law and Order know that when it comes to “getting the bad guy” behind bars, your best chance of success boils down to the strength of your evidence—and the forensic science used to obtain it. Beyond the silver screen, forensic science has been used for decades to help solve even the most tough-to-crack cases.

While growing up in Peace River, Alberta, Trina Moyles heard many stories of Lookout Observers--strange, eccentric types who spent five-month summers alone, climbing 100-foot high towers and watching for signs of fire in the surrounding boreal forest. How could you isolate yourself for that long? she wondered. "I could never do it," she told herself.

Entropy is a law of nature, the one predicting that "things fall apart." Spend enough time outdoors and it will eventually happen to you. When it does, who will pick up the pieces? Who will glue them back together? Professional search and rescue volunteers leave work, home, and their cozy beds to rescue people on the worst day of their lives. They buy their own gear, pay their own gas, and ask nothing more than to make a contribution to the lives of strangers who they'll probably never meet again.

On October 12, 1972, a plane carrying a team of young rugby players crashed into the remote, snow-peaked Andes. Out of the 45 original passengers and crew, only 16 made it off the mountain alive. For 10 excruciating weeks, they suffered deprivations beyond imagining, confronting nature head-on at its most furious and inhospitable. And to survive, these men and women not only had to keep their faith; they had to make an impossible decision: Should they eat the flesh of their dead friends?