Thirteen-year-old Laurie, her family, and her best friend, Jenny, plan to spend a week's vacation in Cabin #13 at the lake in rustic Backbone Park. But the first night, a ghost named Eleanor begins leaving notes warning the vacationers not to stay. Soon, the girls meet teenage brothers Matt and Kevin from cabin #14. Their introduction is more than bumpy as Jenny thoroughly enrages Matt with condescending comments about his confinement to a wheelchair. Nevertheless, the four soon join forces to find out more about the notes. Ranger Roberts tells them that Eleanor, who was also thirteen and occupied Cabin # 13, died the previous summer in a boating accident during the week she was there. He also talks about the strange bobbing lights around the woods and over the water, and the Indian artifacts which he has been finding. A series of notes, coded messages, a canoe accident that was engineered, and information from Eleanor's sister, now incognito, add more clues to the simmering plot that comes to a boil when Laurie deduces the connection between the weird happenings and Ranger Roberts goal to make Backbone an important and popular park.