Readers of master outdoorsman Tristan Gooley have learned that the world is filled with clues to look for--we can use the Big Dipper to tell time, for example, and a budding flower to find south. But what about the innate survival instincts that told Gooley to move on one night, just as he was about to make camp? Everything looked perfect, but something felt wrong. When Gooley returned to his abandoned campsite to search for clues, there they...