In 1911 Leo Denis's book La Verite sur Jeanne d’Arc. (The Truth about Joan of Arc) was published in France. The book postulated that Joan of Arc was psychically gifted and that she can only be truly understood if we accept this. In the introduction of the book the author writes; "To penetrate the mystery of Joan of Arc it seems to us necessary to study, and have practical knowledge of, psychic science. It is necessary to have sounded the depths of this invisible world, this ocean of life which envelops us, from which we all come at birth and into which we are replunged at death. How can writers understand Joan if their thoughts have never risen above terrestrial facts, looked beyond the narrow horizon of an inferior material world, nor caught one glimpse of the life beyond?"
Arthur Conan Doyle, an ardent psychical researcher and a proponent of Spiritualism read the book and was so impressed with it he asked Denis if he could translate it into English. Denis agreed and in 1924 the book was published in London by John Murray under the title, The Mystery of Joan of Arc. Doyle wrote in the introduction; "His (Denis's) treatment of his heroine is so complete that there is no need for me to say anything save to express my personal conviction that, next to the Christ, the highest spiritual being of whom we have any exact record upon this earth is the girl Joan. One would kneel rather than stand in her presence."