"Good God, I'm holding myself responsible for it! It's been hanging over me for nearly a month. And I can't stand much more of it!" "Then let's go back to possibilities. Have you ever checked them over?" "I've gone over 'em like a scrutineer over a voter's list. I've tested 'em all, one by one; but they all end up at the blank wall." "Well, before we go back to these possibilities again, how about the personal equation? Have you any feeling, any emotional bias, any one inclination about the thing, no matter how ridiculous it may seem?" He closed his eyes, and appeared to be deep in thought. "I've always felt one thing," he confessed, "I've always felt--mind you, I only say felt--that when I signed for that Carlton letter, I carried it into Lockwood's own room with his own personal mail, and either gave it to him or left it on his desk." "What makes you feel that?" "In the first place, I must have known he'd seen Carlton recently, and had a clearer idea of his address at the time, than I had. In the second place, being registered, it must have impressed me as being comparatively important." "And Lockwood himself?" "He says I'm mistaken. He holds I never gave him the letter, or he would have remembered it." "And circumstances seem to back him up in this?" "Everything backs him up," was the answer. "Then let's go back to the possibilities. How about theft? Are you sure every one in the office was reliable?" "Every one but _me_!" was his bitter retort. "Then how about its being actually lost inside those four walls?" "That's scarcely possible. I've gone through every nook and drawer and file. I've gone over the place with a fine-tooth comb, time and time again. I've even gone over my own flat, every pocket and every corner of every room." "Then you have a home?" I asked. Again there was the telltale neurasthenic delay before his answer came. "I was married the same week the letter was lost," was his response. "And your wife hasn't been able to help you remember?" "She didn't know of it until a week ago. Then she saw I couldn't sleep, and kept forgetting things, trifling little things that showed I wasn't coordinating properly--such as letting a letter go out unsigned or getting muddled on the safe combination or not remembering whether I'd eaten or not. She said she thought I was in for typhoid or something like that. She went right down to Lockwood and practically accused him of making me overwork. Lockwood had to tell her what had happened. I suppose it was the way it was thrown at her, all in a heap! She went home to her own people that afternoon, without seeing me. I thought it over, and decided there was no use doing anything until--until the mess was cleared up some way or other." I did not speak for several seconds. The case was not as simple as it had seemed. "And Lockwood, how does he feel about it?" I finally asked.