“But I cannot understand,” she said, “how the officers of the law could blunder so.”

“All of the evidence against him,” I said, “was purely circumstantial, except in one particular.  He was in the grounds at the time the murder was committed; your father had quarrelled with him, and it was possible that he had followed you and your father to the house, perhaps not knowing clearly what he was doing, and that another quarrel had occurred.  But that amounted to nothing.  Young men like Swain, even when half-unconscious, don’t murder old men by strangling them with a piece of curtain-cord.  To suppose that Swain did so would be absurd, but for one thing—­no, for two things.”

“What are they?” she demanded.

“One is that the handkerchief which you had tied about his wrist was found beside your father’s chair—­but it was not upon that the jury made its finding.”

“What was it, then?”

“It was this:  Swain swore positively that at no time during the evening had he touched your father.”

“Yes, yes; and that was true.  He could not have touched him.”

“And yet,” I went on slowly, “prints of Swain’s blood-stained fingers were found on your father’s robe.”

“But,” she gasped, pulling her hands away from me and wringing them together, “how could that be?  That is impossible!”

“I should think so, too,” I agreed, “if I had not seen the prints with my own eyes.”

“You are sure they were his—­you are sure?”

“I am afraid there can be no doubt of it,” and I told her how Sylvester had proved it.

She listened motionless, mute, scarce-breathing, searching my face with distended eyes.  Then, suddenly, her face changed, she rose from her chair, flew across the room, opened a book-case and pulled out a bulky volume bound in vellum.  She turned the pages rapidly, giving each of them only a glance.  Suddenly she stopped, and stared at a page, her face livid.

“What is it?” I asked, and hastened to her.

“It is the book of finger-prints,” she gasped.  “A great many—­oh, a great many—­my father collected and studied them for years.  He believed—­I do not know what he believed.”

She paused, struggling for breath.

“Well,” I said; “what then?”

“Mr. Swain’s was among them,” she went on, in the merest whisper.  “They were here—­page two hundred and thirty—­see, there is an index—­’Swain, F., page two hundred and thirty.’”

She pointed at the entry with a shaking finger.

“Well,” I said again, striving to understand, “what of it?”

“Look!” she whispered, holding the book toward me, “that page is no longer there!  It has been torn out!”

Then, with a convulsive shudder, she closed the book, thrust it back into its place, and ran noiselessly to the door leading to the hall.  She swept back the curtain and looked out.

“Oh, is it you, Annie?” she said, and I saw the Irish maid standing just outside.  “I was about to call you.  Please tell Henry to bring those tables and chairs in from the lawn.”