When a fourth child is taken, Solomon Glass knows what to expect: an anonymous letter to the mother, making a promise - kill yourself and your child will be released. He knows because two women are dead already. Glass has just survived his own nightmare - a tragedy, an internal investigation and a spell off the force. In his race to uncover the kidnapper, Glass must enter the darkest side of himself, a place he's barely able to go but where he knows he will find the answers. And the more he learns, the more he suspects that's exactly what the kidnapper wants him to do.