The plot is set into motion with Margaret, a bookseller's daughter, receiving a handwritten letter from the famous yet elusive writer Vida Winter inviting her to come to Winter's home to listen to her secret life story. As the letter explains, Winter has, for the last forty years, spun one strange tale after the other every time someone asked her about her life. Margaret arrives at Winter's, apprehensive, half-expecting yet another fabricated tale, ready to walk away and she almost did until the words pulled her back - "Once upon a time there were twins ---"

