After a miraculous escape from the German military juggernaut in the small Belgian town of Mons in 1914, the first major battle that the British Expeditionary Force would face in the First World War, the British really believed that they were on the side of the angels. Indeed, after 1916, the number of spiritualist societies in the United Kingdom almost doubled, from 158 to 309. As Arthur Conan Doyle explained, 'The deaths occurring in almost...