"'He looked me full in the face and then burst out laughing.' "'You must be mad,' he said; 'I dislike unseasonable jokes.' "'He then went into his bedroom and slammed the door noisily behind him. Half an hour later he had paid the bill, ordered a cab, and gone off with his luggage. He left all your things behind him, madam. Mr. Mainwaring was collected and quiet enough, and seemed quite the gentleman except when he spoke of you; still I don't like the look of affairs at all.' "I listened to my landlady," continued poor Mrs. Mainwaring, "while she told me this strange and most perplexing story. Then I glanced round the room for confirmation of her words. Yes, my husband and all his belongings had vanished, but my work-basket, my new hat, my mantle, my writing-case, and one or two little garments which I was making for the children, were still scattered about the drawing-room. "I went into the bedroom and saw the clothes I had left behind me, flung into a heap in a corner of the room. [Illustration: "TAKE THEM AWAY."] "While I was looking at them in a state of mind almost impossible to describe, my landlady tapped at the door and brought me a note. "'Under the circumstances, madam,' she said, 'you may like to see this letter. I have just found it, stamped and directed as you see, on the davenport in the drawing-room. I think it is in Mr. Mainwaring's writing.' "I took it from her and looked at it eagerly. It was addressed in my husband's writing to a Don of the college (Trinity) where he had taken his degree. I did not hesitate to open it. Here it is, Dr. Halifax; you may like to read it. It may possibly help you to throw some light on this awful mystery." Mrs. Mainwaring gave me the note as she spoke. It contained the following words:-- "MY DEAR SIR,--I much regret having missed you when I called yesterday afternoon to say good-bye. I must take the present opportunity of thanking you for your kindness to me during the whole of my University career. I leave Cambridge by an early train this morning, or would call again to say farewell in person. I hope to call to see you on the first occasion when I revisit Cambridge. "Yours sincerely, "ED. MAINWARING." I read the letter twice, and then returned it without comment to the wife. "Will you redirect it and post it?" I said, after a pause. She answered me almost in a whisper. "The strange thing about that letter is this," she said. "It is addressed to a dead person. Mr. Grainger, Edward's old tutor, has been dead for many years. My husband felt his death keenly when it occurred. He has many times told me of the personal interest Mr. Grainger took in him. Have you no comment to make with regard to this letter, Dr. Halifax?" "I shall have plenty to say in a moment," I answered. "That letter will give us a very important clue to our future actions, but now to proceed: Have you nothing further to tell me?"