The Lookout — Jack Hunt

After escaping near-death, Kelly Danvers, a famed writer with a dark past retreats to a remote, off-the-grid fire lookout in northern Idaho to finish her novel. But when a freak and hostile snowstorm blows in and a lost forest ranger turns up, shivering, and claiming an EMP has destroyed the power grid, trouble soon follows. As Kelly tries to make sense of the danger and make contact with the outside, she quickly finds herself at odds with the stranger, and fighting for survival.