“Yes, Miss Kendall, right here, listening to everything you get a chance to say.  Only be careful.  There is no use spoiling the game by trying to talk to me until you have all that you think you can obtain in the way of evidence.  Don’t let them think you have any means of communication with the outside or they’ll go to any length to silence you.  We’ll be here all the time and the moment you think there is any danger, call us.”

Kennedy seemed visibly relieved by the message.

“She says that she has found out a great deal already, but didn’t dare take the time to tell it just yet,” he explained.  “By the way, Walter, while we are waiting, I wish you would go out and see whether there is a policeman on fixed post anywhere around here.”

Five minutes later when I returned, having located the nearest peg post a long block away on Broadway, Kennedy raised a warning hand.  She was telephoning again.

“She says that attendants come and go in her room so often that it’s hard to get a chance to say anything, but she is sure that there is someone hidden there, perhaps Marie or Madame Margot, whoever she is, or it may even be Betty Blackwell.  They watch very closely.”

“But,” I asked, almost in a whisper, as if someone over there might hear me, “isn’t this a very dangerous proceeding, Craig?  It seems to me you are taking long chances.  Suppose one of the telephone girls in either house, whom she told us keep such sharp watch over the wires, should happen to be calling up or answering a call.  She would hear someone else talking over the wire and it wouldn’t be difficult for her to decide who it was.  Then there’d be a row.”

“Not a chance,” smiled Kennedy.  “No one except ourselves, not even Central, can hear a word of what is said over these connections I have made.  This is what is called a phantom circuit.”

“A phantom circuit?” I repeated.  “What kind of a weird thing is that?”

“It is possible to superimpose another circuit over the four telephone wires of two existing circuits, making a so-called phantom line,” he explained, as we waited for the next message.  “It seems fantastic at first, but it is really in accordance with the laws of electricity.  You use each pair of wires as if it were one wire and do not interfere in the least with them, but are perfectly independent of both.  The current for the third circuit enters the two wires of one of the first circuits, divides, reunites, so to speak, at the other end, then returns through the wires of the second circuit, dividing and reuniting again, thus just balancing the two divisions of the current and not causing any effect on either of the two original circuits.  Rather wonderful, isn’t it?”

“I should say that it was,” I marvelled.  “I am glad I see it actually working rather than have to believe it second hand.”

“It’s all due to a special repeating coil of high efficiency absolutely balanced as to resistances, number of turns of wire, and so on which I have used—­Yes—­Miss Kendall—­we are here.  Now please don’t let things go on too far.  At the first sign of danger, call.  We can get in all right.  You have the evidence now that will hold in any court as far as closing up that joint goes, and I’ll take a chance of breaking into—­well, Hades, to get to you.  Good-bye.