Mercy Merrick is living a difficult life on the streets, but when she meets the young and charismatic clergyman Julian Gray, she desires to leave this life behind and start afresh. She packs her things and volunteers as a nurse in the Franco-Prussian war of 1870. It is, however, very difficult to leave your life behind, and even harder to start a new life in a society so dependent on social connections. So when she sees that Grace Roseberry is killed by a shell, Mercy assumes Grace's identity and social position... - Summary by Carolin