Lee, southeast London. A young girl has disappeared. There are no witnesses, no leads, no clues. The police are tracking a shadow, and time is running out. DI Ellen Kelly is at the top of her game, at least she was, until she took the law into her own hands and confronted her husband's killer. Now she's back at work, leading the investigation into the missing child. Her superiors are watching her; the distraught family is depending on her. Ellen has a lot to prove. And she knows it.