Hold Tight by Harlan Coben

Tia and Mike Baye never imagined they'd become the type of overprotective parents who spy on their kids. But their sixteen-year-old son Adam has been unusually distant lately, and after the suicide of his classmate Spencer Hill - the latest in a string of issues at school - they can't help but worry. They install a sophisticated spy program on Adam's computer, and within days they are jolted by a message from an unknown correspondent addressed to their son - 'Just stay quiet and all safe.'

Meanwhile, browsing through an online memorial for Spencer put together by his classmates, Betsy Hill is struck by a photo that appears to have been taken on the night of her son's death and he wasn't alone. She thinks it is Adam Baye standing just outside the camera's range; but when Adam goes missing, it soon becomes clear that something deep and sinister has infected their community. For Tia and Mike Baye, the question they must answer is this: when it comes to your kids, is it possible to know too much?