"I had with me the magic square which you had made for me, and I began very carefully to work out the problem according to your directions.
"The initial procedure was to put down my theoretical key-sentences, thus:"
| O | N | E | F | O | U | R | T | W | O | F | O | U | R | E | I | G | H | T |
"Underneath I must write the cypher message, and half a dozen letters would be enough to show if I were on the right track. I opened Mr. Fielding Thaneford's old book, and copied down the first seven letters, ranging them vertically under the key-letters. That gave me this arrangement:"
| O | N | E | F | O | U | R |
| Q | W | O | T | T | U | I |
"Now the rule goes on to say that you must find the letter O in the top horizontal column, and follow that column vertically downward until you come to the first cypher letter, in this case Q. The letter at the outside, left end of this second horizontal column, will be the first letter of the original message.
"Well, I tried it, and got the letter B. The next pair yielded an I, which was encouraging, as one would expect a vowel in this position. But the third try gave me a J, and that was not so promising; then I got an N and an E. So far my decoded message read: BIJNE; not very enlightening. The next pair showed the letter U in both key-sentence and cypher. Such a combination is impossible on our magic square, and I had to put down a blank space. The final letter obtained was a Q, and the complete result read: BIJNE-Q. Pure gibberish of course. I tried out a few more pairs, and then gave up in disgust; my beautiful theory had fallen to pieces.
"Just the same, I wasn't ready to give it up. I knew, right in my bones, that old Mr. Thaneford had wanted to tell me something of supreme importance at that last moment on his deathbed, when my hand lay in his and I could feel the intermittent pressure of his fingers. It was impossible that I should be mistaken about any of the figures, for he went over the series three or four times; besides, they did open the safe.
"I was still sure that the numbers meant something more than the mere combination to an old strong-box that held nothing of any pecuniary value. The real secret lay between the covers of that leather-bound book, and I was certain that the old man had been desirous that I should discover it. The Thanefords and the Hildebrands had not been friends for a long while, although nobody knew just why. Probably, it was some ancient grudge Or unforgiven wrong, and old Mr. Thaneford had done his part in keeping it up. But now that he was sick and paralyzed and dying, and especially since he and I had become friends of a sort, he was willing to bury the hatchet. So he told all he could—you remember that he couldn't speak—and he seemed to feel satisfied that I would find the hint sufficient, that I would be clever enough to solve the puzzle.
"And surely it was a puzzle. My best guess had come a flivver, and I didn't see how I could go a step further. Perhaps it was silly to attach so much importance to what the old man had tried to tell me, but I had an intuition that our future happiness and safety were bound up in those crumbling leather covers.