"Making due allowance for feminine hyperbole," he said judicially, "and for the writer's excited state of mind, we arrive at certain definite facts. Here are six deaths--seven if we include that of John Thaneford--and all of them happening under apparently natural but really abnormal conditions. The constant factors in the series of equations are the _locale_ and the general circumstances--an unattended death and no visible cause for dissolution. The period is a variable quantity--from one to over fifty years. We therefore may conclude justifiably that Miss Trevor was wrong in her assertion about something deadly and menacing being always in the room, ready to spring upon its prey. Under that hypothesis the apartment would quickly have become impossible for human occupancy. The alternative theory is that, granting certain conditions, the lethal agent might enter the room and accomplish its deadly purpose, and then immediately withdraw. Finally, this agency might be human or purely mechanical in character. You see what I'm driving at. From the first, I believed that the attack was delivered from without, while Betty and Eunice held that it was what the police call an inside job." "And neither theory was wholly right nor wholly wrong," observed Betty. "Perfectly," rejoined Warriner. "As usual, the truth lay in the middle distance. Now you go on, Betty; this is your part of the story." "My part of the story!" echoed Betty deprecatingly. "I'm not an author; I'm merely the amanuensis, the typist, if you please." "Mock modesty," proclaimed Warriner. "Even now we would still be standing before a closed door were it not for Betty and her master-key." "Yes, my master-key," scoffed Betty. "Only it doesn't seem very clever of me to have carried it all these months without ever thinking to use it." "Perhaps you couldn't find your pocket," suggested Chalmers. "Enough of this bush-beating and persiflage," I commanded severely. "Will you go on and tell me, Betty?" "Well," began my wife obediently, "we had been warned away from the 'Hundred,' but you were obstinate and wouldn't budge; you had to be saved in spite of yourself. "Of course I was right in going North immediately after the Midsummer Night's ball at 'Powersthorp.' Little Hugh really needed the change, and I wanted to be able to call at will on Chalmers for assistance in working out my problem. I couldn't do so if I stayed on at the 'Hundred,' even by means of correspondence. I don't suppose, Hugh, that I need to particularize any further in this direction?" I mumbled something unintelligible, and, to add to my discomfiture, Warriner actually laughed. Never mind; I deserved it all. "I could feel reasonably easy in my mind," went on Betty, "since I knew that the library had been dismantled and locked up. Besides, I had your solemn promise that you would not attempt to enter it for any purpose." "I forgot," I murmured.