Alfred Hitchcock always preferred that his audiences not know much about the stories he told onscreen before the films' conclusion. Of course, this was always made more difficult when the film was based on a book.
In the case of Psycho, Sir Alfred was particularly upset about the secrets behind its ending. So much so that he attempted to buy up every copy of the book he could locate from wholesalers, the publishing house and even any copies he or his secretary might come across in bookstores. The scheme worked; the movie went on to become a huge hit for Mr. Hitchcock.
