With her career on the line following a botched murder investigation, Detective Laura Foster is assigned to investigate the deaths of several homeless people who were living on the streets of London. A murderer is on the loose, killing people seemingly at random. Just when she thinks she might never break the case, however, Laura meets an enigmatic young homeless girl who might just have some of the answers in her notebook. Ophelia refuses to give any information about her past, and won't even reveal her real name. However, she offers to help guide Laura through the labyrinthine world of London's homeless community, as they search for a killer who has nothing left to lose.