Suzanne Perry is having a vivid nightmare. Someone is in her bedroom, touching her, and she can't move a muscle. She wakes, relieved to put the nightmare behind her, but when she opens the curtains, she sees a polaroid stuck to the window. A photo of her sleeping self, taken during the night. With the words: "I'm watching over you". Detective Inspector Phil Brennan of the Major Incident Squad has a killer to hunt. A killer who stalks young women, insinuates himself into their lives, and ultimately tortures and murders them in the most shocking way possible. But the more Phil investigates, Phil realises that it isn't just a serial killer he's hunting but something infinitely more horrific.