It was a sort of disc made of hard rubber for the most part, and about an inch in thickness. Its use was obscure at first glance, but would have been sufficiently plain upon examination. It was a sort of ear trumpet designed for the deaf, but without the old-fashioned horn attachment.
He buttoned his coat once more about him, then proceeded to raise his window the required distance; but at the risk of missing something important, he took his time about it, with the result that the slight sound could not have been heard even a few feet away. When there was room enough for him to crawl through, he did so, and, leaning over, grasped the end of the platform. He stepped noiselessly across the gap, threw one leg over the railing and gently lowered himself to the grating. Along this he tiptoed, his thin-soled shoes making practically no sound as he advanced. In a few moments he was kneeling in front of Stone’s window with the rubber disc held to his right ear, and his ear lowered to the crack at the bottom of the sash.
The wooden wedge was still in place, luckily for him, consequently the sash had remained slightly raised. As soon as the device was brought into use, it amplified the sounds it caught, and what had been an indistinct murmur of voices became an easily audible conversation.
“Be very careful of this,” were the first definite words he heard. They were in Doctor Follansbee’s voice. “I will leave it in the case here for you,” the high, thin tones went on. “Don’t press the plunger until you have inserted the needle underneath the skin. Is that clear?”
“Yes.”
The detective hardly recognized Stone’s voice, so hoarse and agitated did it sound.
“The drug and sponge will be easy for you to handle,” Follansbee explained. “Wait until you get into the room and are six feet or so from the bed, then just sprinkle a few drops on the sponge from this vial.”
“Won’t he smell the stuff and wake up?”
“Certainly not, unless you make a noise. The drug has a penetrating odor, of course, for the time being, but his sleeping sense won’t convey a message of warning soon enough to spoil your plans. If the odor reaches his nostrils before you’re ready to act, and he’s really asleep, it will probably only cause a momentary dream of some sort; an attempt of the subconscious self to explain the situation.”