Just one look. Harlan Coben. 2014.

Grace Lawson is living a happy, straightforward life in the suburbs with her husband, Jack, and two young children.  It that security is about to come to a brutal end. For when Grace picks up a set of holiday snaps, among them is one shot that doesn’t fit: a faded image that Grace doesn’t recognise of her husband as she never knew him.

Within twelve hours, Jack has disappeared and a brutal hitman is stalking his family. All Grace can see is that the past is coming back to haunt the present - and the safe world she knows has been turned upside down.....