“Let’s have another look at the book, anyway. Carmichael said that it was obviously Brotherhood’s copy, because of the queries and things in the margin, but we haven’t even verified that yet.” They were met by an almost uncanny repetition of Reeves’ experience two days before. He had put the paper-bound volume—he was positive that he had put it—in a particular place on his shelves. It was not there, and no amount of search in his rooms could discover it. In despair they sent for Carmichael, to know if for any reason of his own he had resumed possession of what, after all, was his book. He knew nothing of the disappearance; and was inclined to suspect deliberate theft. “You see,” he said, “we never proved that it was Davenant who took away that cipher. We suspected him, of course, when we found that he had been hiding in the secret passage; the exchange of photographs can only be put down to him. But it’s perfectly possible that the cipher was taken away by somebody who simply walked in at the door—somebody who is still in a position to walk in at the door and steal your books, Reeves.” “And that somebody isn’t Davenant. Davenant, poor fellow, is under lock and key.” “It’s a rum thing about that cipher,” said Gordon. “When we’ve got it it doesn’t seem to help us in the least, but whenever we want to get at it, it always seems that the important document has disappeared.” “It’s getting on my nerves,” admitted Reeves. “Seems to me I can’t leave my room without something queer turning up.” “Look here, Carmichael,” said Gordon, “this is where you come in. Get out your stethoscope and go down on all-fours and find clues for us.” “I am afraid that a person entering a room and taking a book away does not commonly leave very much mark on the surroundings. Let’s take a look round, by all means—it’s Sunday, after all, and the housemaid won’t have been dusting. Maids, you will notice, always polish the grates on Sunday but do not dust the rooms; why, I cannot say. Whereabouts did you put the book, Reeves?” “On that shelf there, the top but one.” “It was natural for you to put it there, because it’s within your reach. But you’re tall—I wonder if the other gentleman was shorter? I think a chair would be useful here. . . . Thank you. Yes, he was a good deal shorter. He had to stand on tip-toe to reach the book, and balanced himself, as we all do in such circumstances, by resting the four finger-tips of his left hand on the edge of the shelf beneath. In that way, you see, he could get the forefinger of his right hand on the top of the book. I should say he was a man of about Gordon’s height.” “Unmasked!” cried Gordon, recoiling dramatically. “Send for the Black Maria; I’ll go quiet.”