The house man of the St. Cenis welcomed us cordially upon McBride's introduction and agreed to take us up to the rooms of the strange couple if they were not in. As it happened it was the lunch hour and they were not in the room. Still, Kennedy dared not be too particular in his search of their effects, for he did not wish to arouse suspicion upon their return, at least not yet.
"It seems to me, Craig," I suggested after we had nosed about for a few minutes, finding nothing, "that this is pre-eminently a case in which to use the dictograph as you did in that Black Hand case."
He shook his head doubtfully, although I could see that the idea appealed to him. "The dictograph has been getting too much publicity lately," he said. "I'm afraid they would discover it, that is, if they are at all the clever people I think them. Besides, I would have to send up to the laboratory to get one and by the time the messenger returned they might be back from lunch. No, we've got to do something else, and do it quickly."
He was looking about the room in an apparently aimless manner. On the side wall hung a cheap etching of a woodland scene. Kennedy seemed engrossed in it while the rest of us fidgeted at the delay.
"Can you get me a couple of old telephone instruments?" he asked at length, turning to us and addressing the St. Cenis detective.
The detective nodded and disappeared down the hall. A few minutes later he deposited the instruments on a table. Where he got them I do not know, but I suspect he simply lifted them from vacant rooms.
"Now some Number 30 copper wire and a couple of dry cells," ordered Kennedy, falling to work immediately on the telephones. The detective despatched a bellboy down to the basement to get the wire from the house electrician.
Kennedy removed the transmitters of the telephones, and taking the carbon capsules from them placed the capsules on the table carefully. Then he lifted down the etching from the wall and laid it flat on its face before us. Quickly he removed the back of the picture.
Pressing the transmitter fronts with the carbon capsules against the paper and the glass on the picture he mounted them so that the paper and glass acted as a large diaphragm to collect all the sounds in the room.
"The size of this glass diaphragm," he explained as we gathered around in intense interest at what he was doing, "will produce a strikingly sensitive microphone action and the merest whisper will be reproduced with startling distinctness."