The hours dragged heavily, though it was a splendid chance to observe at leisure the psychology of the shopper who looked at much and bought little, the uncomfortableness of the men who had been dragged to the department store slaughter to say “Yes” and foot the bills, a kaleidoscopic throng which might have been interesting if we had not been so intent on only one matter.

Kennedy grasped my elbow in vise-like fingers.  Involuntarily I looked down at the counter where the Kimberley Queen reposed in all the trappings of genuineness.  Mrs. Willoughby had arrived again.

We were too far off to observe distinctly just what was taking place, but evidently Mrs. Willoughby was looking at the gem.  A moment later another woman sauntered casually up to the counter.  Even at a distance I recognised Annie Grayson.  As nearly as I could make out they seemed to exchange remarks.  The clerk answered a question or two, then began to search for something apparently to show them.  Every one about them was busy, and, obedient to instructions from Donnelly, the store detectives were in the background.

Kennedy was leaning forward watching as intently as the distance would permit.  He reached over and pressed the button near him.

After a minute or two the second woman left, followed shortly by Mrs. Willoughby herself.  We hurried over to the counter, and Kennedy seized the box containing the Kimberley Queen.  He examined it carefully.  A flaw in the paste jewel caught his eye.

“There has been a substitution here,” he cried.  “See!  The paste jewel which we used was flawless; this has a little carbon spot here on the side.”

“One of my men has been detailed to follow each of them,” whispered Donnelly.  “Shall I order them to bring Mrs. Willoughby and Annie Grayson to the superintendent’s office and have them searched?”

“No,” Craig almost shouted.  “That would spoil everything.  Don’t make a move until I get at the real truth of this affair.”

The case was becoming more than ever a puzzle to me, but there was nothing left for me to do but to wait until Kennedy was ready to accompany Dr. Guthrie to the Willoughby house.  Several times he tried to reach the doctor by telephone, but it was not until the middle of the afternoon that he succeeded.

“I shall be quite busy the rest of the afternoon, Walter,” remarked Craig, after he had made his appointment with Dr. Guthrie.  “If you will meet me out at the Willoughbys’ at about eight o’clock, I shall be much obliged to you.”

I promised, and tried to devote myself to catching up with my notes, which were always sadly behind when Kennedy had an important case.  I did not succeed in accomplishing much, however.

Dr. Guthrie himself met me at the door of the beautiful house on Woodridge Avenue and with a hearty handshake ushered me into the large room in the right wing outside of which we had placed the telegraphone two nights before.  It was the library.