“In nearly every office in Maiden Lane where gems and valuable jewelry are stored,” explained McLear, “this electrical system of ours is installed.  When the safes are closed at night and the doors swung together, a current of electricity is constantly shooting around the safes, conducted by cleverly concealed wires.  These wires are picked up by a cable system which finds its way to this central office.  Once here, the wires are safeguarded in such manner that foreign currents from other wires or from lightning cannot disturb the system.”

We looked with intense interest at this huge electrical pulse that felt every change over so vast and rich an area.

“Passing a big dividing board,” he went on, “they are distributed and connected each in its place to the delicate tangent galvanometers and sensitive indicators you see in this room.  These instantly announce the most minute change in the working of the current, and each office has a distinct separate metallic circuit.  Why, even a hole as small as a lead pencil in anything protected would sound the alarm here.”

Kennedy nodded appreciatively.

“You see,” continued McLear, glad to be able to talk to one who followed him so closely, “it is another evidence of science finding for us greater security in the use of a tiny electric wire than in massive walls of steel and intricate lock devices.  But here is a case in which, it seems, every known protection has failed.  We can’t afford to pass that by.  If we have fallen down we want to know how, as well as to catch the burglar.”

“How are the signals given?” I asked.

“Well, when the day’s business is over, for instance, Schloss would swing the heavy safe doors together and over them place the doors of a wooden cabinet.  That signals an alarm to us here.  We answer it and if the proper signal is returned, all right.  After that no one can tamper with the safe later in the night without sounding an alarm that would bring a quick investigation.”

“But suppose that it became necessary to open the safe before the next morning.  Might not some trusted employee return to the office, open it, give the proper signals and loot the safe?”

“No indeed,” he answered confidently.  “The very moment anyone touches the cabinet, the alarm is sounded.  Even if the proper code signal is returned, it is not sufficient.  A couple of our trusted men from the central office hustle around there anyhow and they don’t leave until they are satisfied that everything is right.  We have the authorized signatures on hand of those who are supposed to open the safe and a duplicate of one of them must be given or there is an arrest.”

McLear considered for a moment.

“For instance, Schloss, like all the rest, was assigned a box in which was deposited a sealed envelope containing a key to the office and his own signature, in this case, since he alone knew the combination.  Now, when an alarm is sounded, as it was last night, and the key removed to gain entrance to the office, a record is made and the key has to be sealed up again by Schloss.  A report is also submitted showing when the signals are received and anything else that is worth recording.  Last night our men found nothing wrong, apparently.  But this morning we learn of the robbery.”