How far would you go to snoop on your teenagers if you thought they were in trouble?
That's the issue in this book. Mike and Tia are concerned parents who put a program on their son's computer to track his emails, etc. because he hasn't been himself lately.
From there the action is non-stop. As usual, I enjoyed Coben's writing and the fact that he doesn't preach and leaves the reader to answer the above question for him or herself.