Aurora August is a park ranger - or, that is, she was.
After a bout of mental illness brought on by the stresses of her job and lifestyle threatened her life, she decided it was time to forge a new path. The only problem: she has no idea where to start. Ten years of hard work and a good chunk of her identity had been invested in being a park ranger. Now in her 30s, she finds herself needing to completely reform her sense of self. Feeling isolated in her small mountain town in northwest Montana, she seeks solace at the gym and in nature, the two arenas in which she is most comfortable.
With a new potential job on the horizon, things start to look up...until he shows up. Aurora finds herself trapped by a mysterious stranger whose beastly intentions reveal themselves as she uses every bit of her strength, cunning, and good 'ol ranger know-how to find her way out alive. All the training that has become second nature to her combines with her "take it on the chin" attitude as she is faced with the ultimate puzzle. What once were the very parts of herself that were killing her might now be her tickets to survival.
Meanwhile, Deputy Sheriff William Biel is pulled into the case of a lifetime after an incidental find one otherwise routine morning. This new case hits him harder than any before, not just because of the gravity of what begins to rear its head as he digs deeper, but also a shocking personal connection he never saw coming that may point law enforcement in the right direction. He must team up with Special Agent Amanda Harney of the FBI in the race to find the devil before he can finish his work.