It is 1864 when Lizzie Martin takes up the post of companion to a wealthy widow who is also a slum landlord. Lizzie is intrigued to learn that her predecessor as companion had disappeared, supposedly having run off with an unknown man. But when the girl's body is found in the rubble of one of the recently demolished slums around the prestigious new railway station at St Pancras, Lizzie begins to wonder exactly what has been going on. She has re-made the acquaintance of a childhood friend, now Inspector Benjamin Ross, and with his help starts to investigate, risking her life to unearth the truth about the death of a girl whose fate seems interlinked with her own.