By this time the Senora had reached a public cab stand and had engaged a hack.

Sinking back in the shadows of the top, which was up, Craig directed our driver to follow the hack cautiously, keeping a couple of blocks behind.  There was some satisfaction, though slight, in it, at least.  We felt the possibility of the trail leading somewhere, now.

On uptown the hack went, while we kept discreetly in the rear.  We had reached a part of the city where it was sparsely populated, when the hack suddenly turned and doubled back on us.

There was not time for us to turn and we trusted that by shrinking back in the shadow we might not be observed.

As the hack passed us, however, the Senora leaned out until it was perfectly evident that she must recognize us.  She said nothing but I fancied I saw a smile of satisfaction as she settled back into the cushions.  She was deliberately going back along the very road by which she had led us out.  It had been an elaborate means of wasting our time.

She did not have the satisfaction, however, of shaking us off, for we followed all the way back to the hotel and saw her go in.  Then Kennedy placed the car where we had it before and left the driver with instructions to follow her regardless of time if she should come out again.

Surely, I reasoned, there must be something very queer going on, if they were all it to eliminate us and Norton.  What had happened to him?

Kennedy hastened back to the campus, late as it was, there to start anew.  Norton was not in his quarters and, on the chance that he might have sought to elude Whitney’s detectives by doing the unexpected and going to the Museum, Kennedy walked over that way.

There was nothing to indicate that anybody had been at the Museum, but, as we passed our laboratory, we could hear the telephone ringing inside, as though some one had been trying to get us for a long time.

Kennedy opened the door and switched on the lights.  Waiting only long enough to jam the receiver down into place on the telescribe, he answered the call.

“The deuce you will!” I heard him exclaim, then apparently whoever was talking rang off and he could not get them back.

“Another of those confounded telephone messages,” he said, turning to me and taking the cylinder off.  “I looks as though the ready-letter writer who used to send warnings had learned his lesson and taken to the telephone as leaving fewer clues than handwriting.”

He placed the record on the phonograph so that I could hear it.  It was brief and to the point, as had been the first.

“Hello, is that you, Kennedy?  We’ve got Norton.  Next we’ll get you.  Good-bye.”

Kennedy repeated the first message.  It was evident that both had been spoken by the same voice.

“Whose is it?” I asked blankly.  “What does it mean?”

Before Craig could answer there was a knock at our door and he sprang to open it.