From the New York Times bestselling author of Five Total Strangers and Seven Dirty Secrets, a tense newthriller!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. Butthe 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 ayoung couple with extra supplies on the trail, they're grateful and relievedat first. Riley exudes friendliness, buteverything about her boyfriend Finn spells trouble. That night, after some chilling admissions about Finn fromRiley, Katie and Aster wake to hear the couple fighting. Helpless and trapped in the darkness, they witnessRiley's desperate race into the night, with Finn chasing after.In the morning, they find the couple's camp, but Riley and Finn? Vanished. Katie is sure Riley is in trouble. Andwith help a two-day hike away, they know they are the only ones who can save her before something terriblehappens. The clock is ticking and their supplies are dwindling, but Katie and Aster know they have to find Rileybefore Finnor the desertgets to her first.