Boar Island

National Park Service Ranger Anna Pigeon has handled many kinds of crime, but online harassment is new to her. Elizabeth, the adopted teenage daughter of Anna's friend Heath Jarrod, is the victim. Rumors spread on the internet and abusive texts pile up until Elizabeth is driven to despair.

Heath walks in on Elizabeth in the middle of a suicide attempt that does not succeed. She calls for help from her aunt Gwen and from Anna. The three adults agree that Elizabeth needs to be taken out of the situation while they try to identify whoever is behind the harassment.

Anna is about to start as Acting Chief Ranger at Acadia National Park in Maine, so the group goes with her. They settle into a house on a cliff on Boar Island, a small island near the park. Heath, who is paraplegic, and Elizabeth share it with no one else, since the island is otherwise deserted.

The move does not end the trouble, because the stalker follows them east. Anna has barely arrived at Acadia when a brutal murder is committed, and the killer turns out to be uncomfortably close to her. The book alternates between past and present, and between victims and killers, in a mystery with Anna caught between a fragile teenager and a violent crime.