Like William Mumler, William Hope had his critics. In 1922, the Society for Psychical Research investigated Hope’s practices. They sent investigator Harry Price to Hope’s studio to look into the claims that Hope could materialize spirits through his photography. What Hope didn’t know was that when Price went for his session, the photographic plates he gave to Hope for the session were marked. When Hope developed the images from the session, revealing the ‘spirits’ in the frame with Price, Price was able to prove that Hope switched the plates with his own. Price’s investigation proved Hope’s fraud, although he continued to have some prominent friends come to his defense. Sir Arthur Conan Doyle, the mind behind Sherlock Holmes, defended Hope’s work in The Case for Spirit Photography.