it's riveting, I'm hooked. the tragedy--the emotional impact of what is going on with Tom and Abby four years after Caitlin just disappeared--is so absorbing, and so central to ths book, that I have to remember I'm reading a Thriller; and while always dealing with a sadness, I have to stay alert for twists, and tricks, and surprises. is Tom seeing real things, or is Tom imagining things? what's the actual explanation for Caitlin's disappearance--do I need to suspect characters I've met: Liann? Ryan? Buster? Tracy?