Winner of the Edgar Award for Best Young Adult Novel!From the New York Times bestselling author of Five Total Strangers and Seven Dirty Secrets, a tense new thriller.Four days alone in the desert. Except they're not as alone as they think.A year ago, Katie and her cousin Aster survived a night that left their world and easy friendship fractured. Desperate to heal and leave the past behind them, they tackle four days of hiking in the Utah backcountry. But the desert they've loved for years has tricks up its sleeve.An illness, an injury, and a freak storm leave them short on confidence and supplies. When they come across a young couple with extra supplies on the trail, they're grateful and relieved—at first. Riley exudes friendliness, but everything about her boyfriend Finn spells trouble. That night, after some chilling admissions about Finn from Riley, Katie and Aster wake to hear the couple fighting. Helpless and trapped in the darkness, they witness Riley's desperate race into the ni