"The Woods" by Harlan Coben

Six teenagers, three girls and three boys, go into the woods near their summer camp. Two come out to rejoin their families. Within a short time, two are found dead in different parts of the woods, a half a mile apart. Two have disappeared, presumed dead. Their graves have never been found. The dense woods is large. None of the families will ever be the same again. They go their separate ways.
Twenty years later, the one surviving boy, Paul Copeland, now a successful county prosecutor for Essex County, NJ tells the story. His sister's grave, which his father sought obsessively, has never been found. Two NY police detectives have come to NJ to question Palu's connection to a recent murder victim, a man roughly Paul's age, who had papers on him linking him to Paul. The man's name is totally unfamiliar to Paul. And so the quest begins. What really happened that summer night? Whatever became of Paul's girlfriend, Lucy, the other survivor?
As soon as you think you have the story figured out, something else is revealed, and it is highly plausible. The plot twists and turns and this is a book that is hard to put down.

Watered your mind? yes e