He was surprised at his daughter. It was a completely different Anne from the Anne he had known. There were all kinds of things in her diary which she had never told him. Otto Frank also read that Anne had planned to write a book after the war about her experiences in the secret annexe. He also discovered that she had already rewritten large parts of her diary on loose sheets of coloured paper for that book.

In the book, the van Pels family, Fritz Pfeffer and the helpers were given different names, which Anne had made up. She decided to call the van Pels family the van Daan family. She called Fritz Pfeffer Albert Dussel. Miep Gies became Miep van Santen, Bep Voskuijl became Elli Vossen, Johannes Kleiman was Simon Koophuis, Victor Kugler was Harry Kraler, and so on. Otto Frank used these names as far as possible. In later editions of ‘The Secret Annexe’ (from 1991 onwards) the helpers are referred to by their real names.