Zachary Lynch, because of a traumatic brain injury, can't bear to look at people because he sees not their faces but their true essences. He's the only witness to one of the serial killer's murders, and while he can identify him if he confronts him, he can't recognize him from a picture.
As interesting as the police procedural is in this novel, the relationship between Green and Lynch is even more interesting. Lynch can see things in Green that Green doesn't want to acknowledge about himself.
There's a lot going on in this novel, but Zeltserman meshes everything skilfully while moving the story along like a rocket, and he wraps everything up in under 250 pages. Mark this one up as another big hit in Zeltserman's current winning streak and be sure to check it out when it becomes available next month. You'll be glad you did.