One of the first and finest "sensation novels", the story begins when the protagonist, Walter Hartright, encounters a mysterious woman dressed all in white on a moonlit road in Hampstead. She is confused and in distress, and Hartright helps her to find her way back to London. In return she gives him a warning. Soon after, Hartright learns that she might have escaped from an asylum. The story is told by a succession of character, each with different motivations and agendas.