The War That Saved My Life - Bradley Kimberly Brubaker

Nine-year-old Ada has never left her one-room flat. Her mother is too humiliated by Ada's twisted foot to let her outside. So when her little brother Jamie is shipped out of London to escape the war, Ada doesn't waste a minute - she sneaks out to join him. So begins a new adventure of Ada, and for Miss Susan Smith, the woman who is forced to take in the two children. As Ada teaches herself to ride a pony, learns to read and watches for German spies, she begins to trust Susan - and Susan begins to love Ada and Jamie.