Five women go on a hike. Only four return. Jane Harper, the New York Times bestselling author of The Dry, asks: How well do you really know the people you work with? When five colleagues are forced to go on a corporate retreat in the wilderness, they reluctantly pick up their backpacks and start walking down the muddy path. But one of the women doesn't come out of the woods. And each of her companions tells a slightly different story about what happened. Federal Police Agent Aaron Falk has a keen interest in the whereabouts of the missing hiker. In an investigation that takes him deep into isolated forest, Falk discovers secrets lurking in the mountains, and a tangled web of personal and professional friendship, suspicion, and betrayal among the hikers. But did that lead to murder?