"_Reach him, if possible, at once._ Warn him. Tell him to turn back--to abandon his quest, for death to him is the only alternative. "Do not attempt to trace my identity. _Act_, and _act quickly_, if you wish to prevent a great horror." * * * * * The letter terminated abruptly. Dr. Moore realized in an instant that Oakes's movements were known to some outsider already--someone who had either been in Manhattan that day, or who had sent the letter there to one who had mailed it. He saw the whole matter in a most serious light. Oakes was in danger from forces he did not suspect, perhaps, and the assault he had described had been known to others besides the immediate household of servants. For who, of that household, could have written such a letter? Moore thought of his plans gone astray, of his business engagements, but they all paled into insignificance in the face of the danger to Oakes. He decided to follow up Oakes by the very next train. Finding he had time for one or two calls, he rushed in his carriage to make them, and as he entered his office upon his return he found an energetic young man awaiting him. He knew him as Martin, one of Oakes's aides. "Good evening, Doctor! You're on the rush tonight. My! but I had to hustle." "Good evening! But how did you know so much of my movements--how, why, did you have to hustle?" "I just arrived here a few seconds ago. I have been watching you this evening. Mr. Oakes told me to take care of you and keep you out of mischief. You see, he feared trouble of some kind. I was told to report to you once in a while--and here I am." The physician understood, and then they discussed the recent development. It was agreed that Dr. Moore should leave for Mona; and this, after arranging his business by telephone and hastily making ready, he succeeded in doing. As he boarded the train he asked of Martin, who was with him, if he was to go to Mona also. "That depends upon who enters after you. If I think you are followed, I go too." And Moore realized that Oakes's hand of caution had been shown once more. _CHAPTER VI_ _The Murder_ The rising sun was invisible from the little station hidden in the gloom of the hill, but away out on the river its rays reached the water and marked out sharply the shadow of the high ground. Further down the stream the rugged outlines of the Mansion were cut in silhouette on the surface of the river, which was, as yet, smooth as a mill-pond, but which soon would be moved by those thousands of ripples advancing from the opposite shore. As the sun shot his beams clearer and sharper, the mist of the distance unfolded and the rays struck the ragged granite cliffs of the shore, and revealed them yellow and gray in the bluish haze of the morn. Away up, miles beyond, the river broadened and the mountains of both sides rose abruptly and ruggedly, apparently from the water's edge, causing the effect of a wide, placid lake.