As a National Park Service Ranger, Anna Pigeon has dealt with all manner of crime, but she's out of her depth when the daughter of her friend Heath Jarrod is driven to the edge of suicide by a vicious cyber-bullying campaign.

With Anna about to start her new post at Acadia National Park, Heath decides they will join Anna and stay on a small island nearby—Boar Island. But the move across the country doesn't solve the problem: the stalker follows them east. Making matters worse, a brutal murder is committed soon after Anna’s arrival in Acadia. Now she has friends and park denizens to protect.