"I have read the letter he wrote to you; there is nothing very definite in it," said Quarles. "It was his indefinite state of mind which caused him to relate the whole story to me. When the police failed to make any discovery, he thought some one interested in psychological research might solve the mystery." "What, exactly, were the experiences of this young couple?" I asked. "Chiefly noises, footsteps echoing through a silent house. Once the shadow of a man, or so it seemed, was thrown suddenly upon the wall by a ray of moonlight, and once the curtains and sheets of a bed were found torn, as if hands, finding nothing else to destroy, had taken vengeance upon them. Of course, this all comes second-hand from Dr. Bates." "And is probably unconsciously exaggerated," said Quarles. "The ordinary man is almost certain to overstate and to emphasize unduly one part of the evidence." "That was my feeling exactly," returned Randall, "so I spent a night in that haunted room myself. The result was disappointing." "Did nothing happen?" I asked. "There was no direct manifestation--at least I saw nothing, and I do not think I heard anything, but I am sure that I felt something. It was very vague. You know it is my theory," Randall went on, addressing me, "that different individuals are sensitive to different influences. For example, let us suppose a certain spot is haunted, a spot where something particularly desperate has taken place in the past. Now I believe that A, B, and C, all sensitive to supernatural influences, may watch there and seeing nothing, but that D, being sensitive to that particular influence, or moving on that particular plane, may be successful. In another case, where D fails, A, B, or C may be successful. I think it is this fact which accounts for the comparatively small number of experiences which we are able to authenticate. It was an article of the professor's, setting forth similar views, which made me anxious to make his acquaintance." "Are you suggesting that he should spend a night in this house?" I asked. "I do not think I suggested such a thing," said Randall with a smile, "but I believe that is the professor's intention." "It is," said Quarles. "When?" I asked. "On Friday night." "Greaves died on a Friday night," said Randall. "It is a small point, perhaps, but, like myself, the professor believes in small details." "I suppose the agent will let me have the key," said Quarles. "I do not know the agent. I got the key through Dr. Bates, and I can give you a card of introduction to him."