Kennedy was on his knees, going over the safe with a fine brush and some powder, looking now and then through a small magnifying glass.

“Not a finger print,” he muttered.  “The cracksman must have worn gloves.  But how did he get in?  There isn’t a mark of ‘soup’ having been used to blow it up, nor of a ‘can-opener’ to rip it open, if that were possible, nor of an electric or any other kind of drill.”

“I’ve read of those fellows who burn their way in,” said Schloss.

“But there is no hole,” objected Kennedy, “not a trace of the use of thermit to burn the way in or of the oxyacetylene blowpipe to cut a piece out.  Most extraordinary,” he murmured.

“You see,” shrugged Schloss, “everyone will say it must have been opened by one who knew the combination.  But I am the only one.  I have never written it down or told anyone, not even Muller.  You understand what I am up against?”

“There’s the touch system,” I suggested.  “You remember, Craig, the old fellow who used to file his finger tips to the quick until they were so sensitive that he could actually feel when he had turned the combination to the right plunger?  Might not that explain the lack of finger prints also?” I added eagerly.

“Nothing like that in this case, Walter,” objected Craig positively.  “This fellow wore gloves, all right.  No, this safe has been opened and looted by no ordinarily known method.  It’s the most amazing case I ever saw in that respect—­almost as if we had a cracksman in the fourth dimension to whom the inside of a closed cube is as accessible as is the inside of a plane square to us three dimensional creatures.  It is almost incomprehensible.”

I fancied I saw Schloss’ face brighten as Kennedy took this view.  So far, evidently, he had run across only skepticism.

“The stones were unset?” resumed Craig.

“Mostly.  Not all.”

“You would recognize some of them if you saw them?”

“Yes indeed.  Some could be changed only by re-cutting.  Even some of those that were set were of odd cut and size—­some from a diamond necklace which belonged to a—­”

There was something peculiar in both his tone and manner as he cut short the words.

“To whom?” asked Kennedy casually.

“Oh, once to a well-known woman in society,” he said carefully.  “It is mine, though, now—­at least it was mine.  I should prefer to mention no names.  I will give a description of the stones.”

“Mrs. Lynn Moulton, for instance?” suggested Craig quietly.

Schloss jumped almost as if a burglar alarm had sounded under his very ears.  “How did you know?  Yes—­but it was a secret.  I made a large loan on it, and the time has expired.”

“Why did she need money so badly?” asked Kennedy.

“How should I know?” demanded Schloss.

Here was a deepening mystery, not to be elucidated by continuing this line of inquiry with Schloss, it seemed.