If I speak of myself in this story, it is because I have been deeply involved in its startling events, events doubtless among the most extraordinary which this twentieth century will witness. Sometimes I even ask myself if all this has really happened, if its pictures dwell in truth in my memory, and not merely in my imagination. In my position as head inspector in the federal police department at Washington, urged on moreover by the desire, which has always been very strong in me, to investigate and understand everything which is mysterious, I naturally became much interested in these remarkable occurrences.