Kennedy lapsed into thought.  Who could the self-constituted watcher have been?  Who was interested in this case other than the proper authorities?  Apparently some one knew more than Mackay, more than Kennedy.  Whoever it was had made no effort to communicate with any of us.  This was a new angle to the mystery, a mystery which became deeper as we progressed.

At the house Kennedy first made a careful tour of the exterior, but found nothing.  Mackay had doubled his guards and had sent Phelps’s servants away so that there could be no interference.

Once inside, I noticed that Kennedy seemed indisposed to make another minute search of the library.  He went over the frame of the French window with his lens carefully, for fingerprints.  Finding nothing, he went back directly to the portieres.

For several moments he stood regarding them in thought.  Then he began a most painstaking inspection of the cloth with the pocket glass, beginning at the library side.

I remembered that first scene in the manuscript which Kennedy had insisted I read.  I recalled the suspicion which had flashed to me before the message from Mackay had disturbed both Kennedy’s thoughts and mine.  Stella Lamar had thrust her bare arm through this curtain.  A needle, cleverly concealed in the folds, might easily have inflicted the fatal scratch.  It was for a trace of the poison point that Kennedy searched.  Of that I was sure, knowing his methods.

I glanced up and down the heavy hanging silk, looking for the glint of fine sharp steel as Kennedy had done before starting his inspection with the glass.  The color of the silk, a beautiful heavy velour, was a strange dark tint very close to the grained black-brown of the woodwork.  Both the thickness of the material and its dull shade made the portieres serve ideally for the purpose assumed now both by Kennedy and myself.  A tiny needle might remain secreted within their folds for days.  Nothing, certainly, caught my naked eye.

At last a little exclamation from Kennedy showed us that he had discovered something.  I moved closer, as did Mackay.

“It’s lucky none of us toyed with these curtains yesterday,” he remarked, with a slight smile of gratification.  “There might have been more than one lying where Stella Lamar lies at the present moment.”

With wholesome respect neither Mackay nor myself touched the silk as Kennedy pointed.  There were two small holes, almost microscopic, in the close-woven material.  About the one there was the slightest discoloration.  Not a fraction of an inch away I saw two infinitesimal spots of a dark brownish-red tinge.

“What does it mean?” I asked, although I could guess.

“The dark spots are blood, the discoloration the poison from the needle.”

“And the needle?”

He shrugged his shoulders.  “That’s where our very scientific culprit has forestalled me, Walter!  The needle was in these curtains all day yesterday.  Unfortunately, I did not study the manuscript, did not attach any importance to Miss Lamar’s scene at the portieres.”