When we reached the entrance to our quarters on Montgomery Street the rain had once more begun to fall, gently now, but the gusts of damp wind from the south promised more and worse to follow. “Hello!” cried the first man, starting back. “What's this?” The line stopped, and I moved forward. “What is it?” I asked. “A message for you, Mr. Wilton,” said a voice suddenly from the recess of the doorway. “Give it to me,” I said. A slip of paper was thrust into my hand, and I passed up the stairs. “I'll wait for you,” said the messenger, and at the first gas-jet that burned at the head of the stairs I stopped to read the address. It was in the hand of the Unknown, and my fatigue and indifference were gone in a moment. I trembled as I tore open the envelope, and read: “Follow the bearer of this note at 12:30. Come alone and armed. It is important.” There was no signature. If this meant anything it meant that I was to meet the Unknown, and perhaps to search the heart of the mystery. I had been heavy with fatigue and drowsy with want of sleep, but at this thought the energies of life were once more fresh within me. With my new-found knowledge it might be more important than even the Unknown was aware, that we should meet. To me, the map, the absence of Darby Meeker and his men, the mysterious hints of murder and death that had come from the lips of Mother Borton, were but vaguely suggestive. But to the Unknown, with her full knowledge of the objects sought by the enemy and the motives that animated their ceaseless pursuit, the darkness might be luminous, the obscurity clear. The men had waited a minute for me as I read the note. “Go to your rooms and get some rest,” I said. “I am called away. Trent will be in charge, and I will send word to him if I need any of you.” They looked at me in blank protest. “You're not going alone, sir?” cried Owens in a tone of alarm. “Oh, no. But I shall not need a guard.” I hoped heartily that I did not. The men shook their heads doubtfully, and I continued: “Corson will be down from the Central Station in fifteen or twenty minutes. Just tell him that I've been sent for, and to come to-morrow if he can make it in his way.” And bidding them good night I ran hastily down the stairs before any of the men could frame his protest into words. “Are you ready, sir?” asked the messenger. “It is close on half-past twelve,” I answered. “Where is she?” “It's not far,” said my guide evasively. I understood the danger of speech, and did not press for an answer.