“Well,” said Gatton, looking at me oddly, “in addition to the texture of the curtain do you notice anything else?”

“No,” I confessed.

“Well,” he continued, “you may remember that yesterday when I examined this place, I had to drape the curtain over a chair, which I moved here for the purpose, in order to see the recess.”

“So you did,” I said; “I remember.”

“Well, doesn’t it strike you as odd?  If you’ll notice the way it is fastened above, you will see that it is not upon rings.  In other words it is not intended to be opened.  You see that it is in one piece so that anybody having occasion to enter the recess would have to lift it aside and let it fall to behind him.”

I studied the arrangement of the drapings more closely and saw that his statement was correct; also I saw something else, and: 

“This room has been lighted by gas at some time!” I cried.  “Here, up under the picture-rail, is a plug.”

“Most houses are provided both with gas and electric light about here,” replied Gatton abstractedly.

But even before he had finished speaking I saw his expression change, and in a moment he had dragged a chair into the recess.

“Hold the curtain back,” he directed sharply.

Standing on the chair, he began to examine the little brass plug to which I had drawn his attention.  For some time I watched him in silence, and then: 

“What do you think you have found?” I inquired.

He glanced down over his shoulder.

“I think I have found a clew!” he replied.

CHAPTER X

“HANGING EVIDENCE”

Isobel came into the room and approached the chair from which I had arisen.  In her plain morning frock, with the sun bringing out those wonderful russet tints in her hair, but having that frightened look still in her eyes, she had never seemed more beautiful.  Yet I saw as I rose to greet her that she was laboring under the influence of dangerous nervous excitement.

“You are worried about Eric?” I said, when we had exchanged those rather formal greetings in which I think we took mutual shelter.  Certainly I did, and later I was to know that Isobel did so, too.

“Every day seems to make the case grow blacker against him,” she replied, sinking down upon the settee beside me.

And indeed the shadow which had fallen upon all of us seemed at that moment almost palpable—­a thing to be felt like the darkness of Egypt and not to be dispelled even by the brightness of the morning.

“When did you last see Coverly?”

Isobel raised her head wearily.

“Last night, and he seemed to think that some one was following him—­a detective.”

I noticed that Isobel spoke of Eric Coverly with a certain manner of restraint for which I could not account.  Yet perhaps it was only natural that she should do so, but at the time I was foolishly blind to the opposing emotions which fought and conflicted within her.