When Isobel Crawley asks Violet Crawley how she's feeling, Violet replies, "Like Dr. Manette. If I don't get out of this house soon, I shall remember nothing but my number." This is a reference to Charles Dickens' novel, A Tale of Two Cities. In the book, Dr. Manette is wrongfully emprisoned for 20 years. As a result, he gets amnesia and remembers only his assigned prison number.