Born into poverty and living under the roof of her violent and abusive brother-in-law, young Kitty Cox dreams of working in a women's dress shop in the West End - a million miles away from the reality of her life as a mud-lark, scavenging on the banks of the Thames. Fate soon intervenes and Kitty finds herself working as a skivvy for Sir Desmond and Lady Arabella Mableton in Mayfair. Bullied by the kitchen maids, Kitty is soon taken under Lady Arabella's wing and for the first time in her life Kitty dares to hope. But Lady 'Bella' has a secret and unable to live with her domineering husband she decides to leave, fighting for custody of their daughter, Leonie. Kitty will do anything for her mistress but her loyalty is severely tested as all their lives are thrown into turmoil and Kitty faces a life of poverty and hardship in the slums of the East End once more.