Alex knows she risks getting fired from her law firm if she takes on another unpaid case, but when she hears Rosa's desperate voice at the other end of the phone, she knows she has to help - the body of Rosa's shy teenage sister, Natalia, has been dragged, lifeless, from the Thames. Alex can't help but think of her own missing little sister. She knows how a lack of answers can eat you alive. Kat has worked hard to become Special Adviser to the Home Secretary, and is eager to finally put the dark and tragic part of her past behind her. But when she discovers a series of cover-ups, she begins to wonder whether her seemingly perfect new boss could be involved. Then she's shocked to discover a letter that raises worrying questions about a girl found drowned in London.