"There is no object whatever to be gained by adopting your suggestion," it ran. "The only absolutely safe course is to continue as in the past. The silence is effectual, and for the present is enough. All your fears are quite groundless. Show a bold front and be cautious always. If you wish to write, send your letter to the old address." Each of the others were similarly unintelligible, except perhaps the later one, in which the writer said: "You are right. I, too, have discovered cause for apprehension. A peril threatens, but if the secret is preserved it cannot harm us." With the mass of papers and correspondence spread before us we all three examined these suspicious letters very carefully. In the drawer which Boyd had opened was, among other things, a few girlish trinkets and souvenirs of the past, and a note signed "Mary Blain," and dated from Riverdene a couple of months before. In the face of recent events it was a somewhat noteworthy missive, for beginning "Dearest Eva," it gave her an invitation for tennis on the following day, Tuesday. "I have also your admirer," she went on, "and he will no doubt come. Perhaps I shall be compelled to go to town to-morrow afternoon on business, the urgent nature of which you may guess. If I do I will convey your message to the quarter for which it is intended. Be careful how you act, and what you say to F," (meaning, I suppose, myself), "for I have no great faith in him. His friend is, of course, entirely well-disposed towards us." I passed it to Boyd, and when he had read it, asked-- "What's your opinion of that? Is the person mentioned myself? and is the friend actually Dick?" "It really seems so," he responded, with knit brows. "In that case they must have long ago suspected you of being aware of their secret. This would, of course, account for the cowardly attempt to take your life." "By means of this unknown drug here--eh?" I suggested bitterly, pointing to the small box which I had a moment before closed. "Certainly," said the detective. "There can now be no further doubt of Miss Glaslyn's complicity in the affair." "I wonder who is the author of these type-written letters?" I said. "If we knew that, it would let a flood of light into the whole matter." "We shall, I hope, discover that in due course," he answered. "Let's finish these investigations before discussing our next move," and he continued, carefully placing back the letters in the secret drawers, now and then pausing to re-read one which chanced to attract his attention. "Look at this," he said, passing one over to me after he had glanced at it. It was written on pale green paper in a fine fashionable woman's hand, a few brief lines, which ran:--