He paused a moment to note the breathless interest of Pender’s face and manner.  Every word he uttered was calculated; he knew exactly the value and effect of the emotions he desired to waken in the heart of the afflicted being before him.

“And from certain knowledge I have gained through various experiences,” he continued calmly, “I can diagnose your case as I said before to be one of psychical invasion.”

“And the nature of this—­er—­invasion?” stammered the bewildered writer of humorous tales.

“There is no reason why I should not say at once that I do not yet quite know,” replied Dr. Silence.  “I may first have to make one or two experiments—­”

“On me?” gasped Pender, catching his breath.

“Not exactly,” the doctor said, with a grave smile, “but with your assistance, perhaps.  I shall want to test the conditions of the house—­to ascertain, impossible, the character of the forces, of this strange personality that has been haunting you—­”

“At present you have no idea exactly who—­what—­why—­” asked the other in a wild flurry of interest, dread and amazement.

“I have a very good idea, but no proof rather,” returned the doctor.  “The effects of the drug in altering the scale of time and space, and merging the senses have nothing primarily to do with the invasion.  They come to any one who is fool enough to take an experimental dose.  It is the other features of your case that are unusual.  You see, you are now in touch with certain violent emotions, desires, purposes, still active in this house, that were produced in the past by some powerful and evil personality that lived here.  How long ago, or why they still persist so forcibly, I cannot positively say.  But I should judge that they are merely forces acting automatically with the momentum of their terrific original impetus.”

“Not directed by a living being, a conscious will, you mean?”

“Possibly not—­but none the less dangerous on that account, and more difficult to deal with.  I cannot explain to you in a few minutes the nature of such things, for you have not made the studies that would enable you to follow me; but I have reason to believe that on the dissolution at death of a human being, its forces may still persist and continue to act in a blind, unconscious fashion.  As a rule they speedily dissipate themselves, but in the case of a very powerful personality they may last a long time.  And, in some cases—­of which I incline to think this is one—­these forces may coalesce with certain non-human entities who thus continue their life indefinitely and increase their strength to an unbelievable degree.  If the original personality was evil, the beings attracted to the left-over forces will also be evil.  In this case, I think there has been an unusual and dreadful aggrandisement of the thoughts and purposes left behind long ago by a woman of consummate wickedness and great personal power of character and intellect.  Now, do you begin to see what I am driving at a little?”