The manner in which I became intimately associated with a fearful mystery with which not only all London but all England was ringing, and the strange, inexplicable Being whom the course of events brought to my knowledge, are so startling and wonderful, that I have grown to believe that by no effort of the imagination, however wild and bewildering the labyrinths into which it may lead a man, can the actual realism of our everyday life be outrivalled. What I am about to narrate is absolutely true-