Abandoned at the gates of a London park one winter's night in 1850, baby Lily Mortimer is saved by a young police constable and taken to the London Foundling Hospital. Across the years, policeman Sam Trench keeps watch over the young woman he once saved. When Sam meets Lily again, there is an instant attraction between them and Lily is convinced that Sam holds the key to her happiness - but might he also be the one to uncover her crime and so condemn her to death?