Hold Tight by Harlan Coben

NOW A NETFLIX SERIES!
The bestselling author and creator of the hit Netflix dramas Stay Close and The Stranger delivers a #1 New York Times bestseller that asks how well parents really know their children—and puts them on a technological roller coaster of their worst fears.
"We're losing him." With those words, Mike and Tia Baye decide to spy on their sixteen-year-old son Adam, who has become increasingly moody and withdrawn since the suicide of his best friend. The software they install on his computer shows them every Web site visited, every e-mail sent or received, every instant message. And each keystroke draws them deeper and deeper into a maze of mayhem and violence that could destroy them all....