When the campaign around Richmond intensified, the prison commandant clamped down on visitors, forbidding any conversation during visits. Undeterred by the strict prison rules, Van Lew found ways to continue her intelligence swap with the prisoners. She realized, for example, that the books she frequently brought for the prisoners could offer a variety of ways to exchange information. She could tuck enciphered messages down a book's spine. She also developed another way of using books to conceal secret messages. She opened a book to a prearranged page and made a pinhole above each letter on that page that spelled out her secret message. Prisoners could easily respond in the same way.