After secrets and betrayal shatter his marriage, Josh Mallory seeks solace on the Pacific Crest Trail, in the mountains of Washington. On the trail, he's just another hiker. On the trail, he can outrun the memories. But this backpacking trip swiftly turns grisly when he comes across the body of another hiker who seems to have fallen to his death. Josh is forced to detour through a small mountain town, where missing hiker posters flutter in the windows, and residents show no interest in hearing about the dead hiker. Unease that something is not quite right chases him back to the trail.

But night falls too quickly and in his haste to get away, he becomes trapped on a mountain ridge beneath the light of a full moon. Feeling more and more uneasy, Josh soon realizes that he may not be alone on the mountain, and begins to fear that, like the missing hikers, he won't make it out alive.