“You therefore placed a chair in front of the door to stand on and opened the transom over the door. After tying a handkerchief over your mouth and nostrils, you raised the cover of a little box you had brought with you and released a bat in the room. Then you closed the transom and departed from the house as silently as you had entered it.
“The bat proved to be a faithful ally, Monsieur. On little rubber pads that you had glued on the upper side of its wings was a preparation used by the Dyaks to poison the tips of their arrows and spears. The preparation, which you used in powdered form, with a few added ingredients of your own, as employed by the Dyaks, consists of a paste made from the milky sap of the upas tree, dissolved in a juice extracted from the tuba root. With one possible exception, it is the most deadly poison known, a minute quantity, breathed in through the nostrils or absorbed into the system through an abrasion on the skin, causing almost instant death.
“When you released the bat in the library, it began to circle around the room and its fluttering wings scattered the powder and poisoned the air to such an extent that poor Berjet had only time, before he died, to realize the significance of the bat’s presence in the room and to leap through the window in a vain effort to save himself.
“You, in the meantime, had walked slowly down the street, and when the scientist catapulted himself through the window-sash, you were calmly lighting a cigarette under the corner lamp post half a block away. The complication was one you doubtless had not anticipated; you had thought that Berjet would die an instant death when he got a whiff of the powder.
“Nevertheless, you had nothing to fear, you thought; you had laid your plans too carefully. Like any innocent pedestrian would be expected to do, therefore, you ran back down the street, determined to be in at the finish, to see your work well done.
“All this time the bat—whose mouth and nostrils, by the way, you had protected with a tiny gauze mask from which the creature could eventually free itself—was no doubt flying around and around, trying to find egress from the room. It was while you were standing on the pavement in front of the house, talking with Sprague and Greenleigh, that the bat discovered the broken window-sash and escaped into the open air.
“As it winged its way aimlessly over the sidewalk, it flew close enough to Sprague to scatter some of the powder in his face, and an instant later, continuing its flight, it passed in front of you.
“Dr. Sprague inhaled a fatal amount of the powder, but you breathed in only enough to throw you into a kind of convulsion. The struggles of both you and the physician to get your breath and otherwise to overcome the seizure made it appear that you were grappling with an invisible antagonist. Sprague succumbed almost instantly; but you, after a brief struggle, recovered, and in order to throw me off the track, as you believed, cleverly conceived the ‘invisible monster.’
“Nor did you have to draw much upon your imagination for the ‘whispering sound’ and the ‘icy breathing’ of the unholy creature of your mind. The whir of the bat’s wings as it flew past you made a sound not unlike that of a sibilant whisper, while the whiffs of air that the animal’s wings fanned against your cheek, suggested the ‘cold and clammy breathing’ of the mythical monster.
“Ma foi! well do I know whereof I speak, Monsieur, for I heard the ‘whisper’ and felt the ‘breath’ of the Thing myself. The bat that was loosed in my room last night gave me the fright of my life. When its wings brushed against the wall it sounded like a whisper of the devil himself, and when its wings fanned the air against my face, I thought a corpse was breathing death into my soul. No coward am I, monsieur, but the ‘whispering’ and ‘breathing’ were so terribly real—which only goes to show what suggestion will do to a vivid imagination. You had talked so earnestly and so picturesquely about the ‘whisper’ and the ‘breath’ of the Thing, that when I first heard the whir of the little animal’s wings in the inky-dark room—Dame! It makes me shiver yet!