The God of the Woods by Liz Moore

Some said it was tragic, what happened to the Van Laars. Some said the Van Laars deserved it. That they never even thanked the searchers who stayed out for five nights in the freezing forest trying to help find their missing son. Some said there was a reason it took the family so long to call for help. That they knew what happened to the boy. Now, fifteen years later, their daughter has gone missing in the same wilderness as her brother. Some say the two disappearances aren't connected. Some say they are.