“What is the cipher system?” I asked, mechanically, my head rather in a whirl at the fast-crowding events.
“Don’t you understand?” he cried, almost gleefully, working at the solution of the secret writing. “I’ve got it! How stupid of me before not to think of it. Why, it’s the old checkerboard cipher again!”
Quickly he drew on paper a series of five squares horizontally and five vertically and filled them in with the letters of the alphabet, placing I and J in the same square, thus using twenty-five squares. Over the top he wrote the numbers to 5 and down the side he did the same, as follows:
| 1 | 2 | 3 | 4 | 5 | |
| 1 | A | B | C | D | E |
| 2 | F | G | H | IJ | K |
| 3 | L | M | N | O | P |
| 4 | Q | R | S | T | U |
| 5 | V | W | X | Y | Z |
“Do you see?” he cried, eagerly. “The letter ‘e’ is in the first row, the fifth letter—15. The letter ‘n’ is the third letter in the third row—33. Why, it’s simple!”
It might have been simple to him now, but to Hastings and myself, as Kennedy figured the thing out, it was little short of marvelous. For all we could have done it, I suppose the blank scrap of paper would still have been a hidden book.
We were crowded about Kennedy, eagerly watching what his deciphering might yield, when the office-boy announced, “Mr. Shelby Maddox to see you, Mr. Hastings.”
Kennedy quickly covered the papers on which he was writing with some others on the desk, just as Shelby entered.
“Is Kennedy here?” cried Shelby. “Oh—I thought maybe you might be. They told me that you’d gone early to the city.”
Our greeting was none too cordial, but Shelby either did not notice it or affected not to do so.