That was the beginning. The details of me are not important here; I need only say that I was twenty-four that summer. Dora and I were engaged to be married. Both of us were orphans. She was wealthy; I was not, so that I did not want to marry until I had made a success of an invention on which I was working--a ray-weapon with which I hoped, not to make war more deadly, but to make war impossible. It was a non-killing, paralyzing vibration. In theory, if I could project it any great distance--a vibration on speeding form--then with it whole armies would be stricken down, rendered helpless. But I had not progressed that far as yet. I was living in Dora's home, working in a small laboratory with which it was equipped. Just this week I had completed a miniature projector. With tests upon animals it seemed to be effective at some fifty feet.... Dora's home was some three miles out in the country from the Crossroads Municipal Village where we had gone to hear the music. We took her little air-roller which was parked nearby. We did not fly it for such a short distance, merely rolled it out on the State Road. Dora was frightened, but I tried to shrug away the mysterious incident. "That--that little thing that stood watching us," she said. "Oh Tom--" "Looked like a boy with an overcoat over his head," I told her. "Forget it, Dora." Had she noticed that the man who had accosted us knew her name? She did not mention it, nor did I. We were approaching her home within five minutes. Here, fifty miles north of New York City, there was one of the infrequent patches of lonely country. Her small cement and metal cottage nestled against a wooded hillside. Queer--as we rolled up, the house was in complete darkness. Yet Mrs. Holten, our housekeeper, certainly would not have retired now at ten o'clock. We stopped at the main entrance and climbed out. "Oh Tom--" Dora murmured. "Something very strange about this--" She stood clinging to me, with the dark silent house beside us. Overhead the moon was riding a sky of low, swift-flying clouds. The trees around the house stirred with a night breeze, but beyond that it seemed that everything was abnormally silent--a silence hanging menacingly around us. "Mrs. Holten must have gone to bed," I said. "Come on, let's go in." But Mrs. Holten wasn't in the house. We called; then lighted all the lights. The place was in perfect order, but the housekeeper was gone. "Strange," I said. "I suppose something called her away. She should have left us a note." But what I didn't say was that on the wall of the hall, near the door of the laboratory there were dark marks on the plaster--marks that suggested a burn, as though heat had struck the wall. "Tom, come here," Dora called from the living room. "What a queer smell!" I met her frightened gaze; her nostrils were dilating. I could smell it--an acrid, pungent smell.