Over the safe in back was a framework like that which had covered Schloss’ safe.  Kennedy tore it away, regardless of the alarm which it must have sounded.  In a moment he was down before it on his knees.

“This is how Schloss’ safe was opened so quickly,” he muttered, working feverishly.  “Here is some of their own medicine.”

He had placed the peculiar telephone-like transmitter close to the combination lock and was turning the combination rapidly.

Suddenly he rose, gave the bolts a twist, and the ponderous doors swung open.

“What is it?” I asked eagerly.

“A burglar’s microphone,” he answered, hastily looking over the contents of the safe.  “The microphone is now used by burglars for picking combination locks.  When you turn the lock, a slight sound is made when the proper number comes opposite the working point.  It can be heard sometimes by a sensitive ear, although it is imperceptible to most persons.  But by using a microphone it is an easy matter to hear the sounds which allow of opening the lock.”

He had taken a yellow chamois bag out of the safe and opened it.

Inside sparkled the famous Moulton diamonds.  He held them up—­in all their wicked brilliancy.  No one spoke.

Then he took another yellow bag, more dirty and worn than the first.  As he opened it, Mrs. Moulton could restrain herself no longer.

“The replica!” she cried.  “The replica!”

Without a word, Craig handed the real necklace to her.  Then he slipped the paste jewels into the newer of the bags and restored both it and the empty one to their places, banged shut the door of the safe, and replaced the wooden screen.

“Quick!” he said to her, “you have still a minute to get away.  Hurry—­anywhere—­away—­only away!”

The look of gratitude that came over her face, as she understood the full meaning of it was such as I had never seen before.

“Quick!” he repeated.

It was too late.

“For God’s sake, Kennedy,” shouted a voice at the street door, “what are you doing here?”

It was McLear himself.  He had come with the Hale patrol, on his mettle now to take care of the epidemic of robberies.

Before Craig could reply a cab drew up with a rush at the curb and two men, half fighting, half cursing, catapulted themselves into the shop.

They were Winters and Moulton.

Without a word, taking advantage of the first shock of surprise, Kennedy had clapped a piece of chemical paper on the foreheads of Mrs. Moulton, then of Moulton, and on Muller’s.  Oblivious to the rest of us, he studied the impressions in the full light of the counter.

Moulton was facing his wife with a scornful curl of the lip.

“I’ve been told of the paste replica—­and I wrote Schloss that I’d shoot him down like the dog he is, you—­you traitress,” he hissed.

She drew herself up scornfully.