One girl disappears. And there's a link to an unsolved disappearance close to home. Katies Wells goes missing on her way to school. Her pink backpack is found weighed down with stones in a local reservoir. Time is running out to find her, and every second counts. Acting DCI Rob Miller leads a nationwide search, but no trace of the little girl is found. Meanwhile, Detective Jo Maguire from the National Crime Agency notices striking similarities to her own sister's disappearance twenty years ago. Jo's relationship with Rob is deepening, but they don't have time to figure things out. Maybe Jo's sister was the killer's first victim. And maybe he never stopped. Now, a body is discovered and the public holds its breath. Is it Katie? Rob and Jo might have a serial killer on their hands...