I stopped tapping the keys and wheeled unexpectedly about in my chair.  I am sure that I caught just a fleeting glimpse of a face dodging back from the window, which was on the first floor.

Whose face it was I am not prepared to assert exactly.  But there was a face, and the fleeting glimpse of the eyes and forehead was just enough to give me the impression that they were familiar, without enabling me to identify them.  At any rate, the occurrence made me feel decidedly uncomfortable, especially after the warning letters that we had all received.

I sprang to my feet and ran to the door.  But it was too late.  The intruder had disappeared.  Still, the more I thought about it, the more determined I was to try to verify an indistinct suspicion, if possible.  I put on my hat and walked hurriedly over to the office of the registrar.

Sure enough, I found that Alfonso de Moche had been at the University that day, must have attended a lecture an hour or so before.  Having nothing else to do, I hunted up some of his professors and tried to quiz them about him.

As I had expected, they told me that he was an excellent student, though very quiet and reserved.  His mind seemed to run along the line of engineering, and particularly mining.  I could not help coming to the conclusion that undoubtedly he, too, was infected by the furore for treasure hunting, in spite of his Indian ancestry.

Yet there seemed to be surprisingly little known about him outside of the lecture room and laboratory.  The profesors knew that he lived with his mother at a hotel downtown.  He seemed to have little or nothing to do with the other students outside of class work.  Altogether he was an enigma, as far as the social life of the University went.  It looked very much as though he had come to New York quietly to prepare himself for the search for the buried treasure.  Had the Gold of the Gods lured him into its net, too?

Reflecting on the tangle of events, the strange actions of Lockwood and the ambitions of Whitney, I retraced my steps in the direction of the laboratory, convinced that de Moche had employed at least a part of his time lately in spying on us.  Perhaps he had seen Inez going in and out.  Suddenly it flashed over me that the interchange of glances between de Moche and Lockwood indicated that she was more to him than a mere acquaintance.  Perhaps it had been jealousy as well as treasure hunting that had prompted his eavesdropping.

Still reflecting, I decided to turn in at the Museum and have a chat with Norton.  I found him nervously pacing up and down the little office that had been accorded him in his section of the building.

“I can’t rid my mind of that warning,” he remarked anxiously, pausing in his measured tread.  “It seems inconceivable to me that any one would take the trouble to send four such warnings unless he meant it.”

“Quite so,” I agreed, relating to him what had just happened.