"Of course I do," I answered eagerly. "The extra O in your original key-sentence is not only wrong in itself, but its inclusion in the series throws everything which follows it into hopeless confusion. Let's try it out."
Rapidly I wrote down the correct key-letters, and underneath them a score of the cypher symbols, thus:
| W | O | N | F | O | R | T | O | F | O | R | A | T | E | W | O | N | F | O | R | T |
| Q | W | O | T | T | U | I | J | X | I | S | V | A | Z | P | I | H | N | X | J | X |
Taking up the magic square I asked Betty to repeat the formula for uncoding.
"Find where the first key-letter occurs in the top row," said Betty glibly. "For example: W. Then follow that vertical column down until you reach the first letter of the cypher message; in this case: Q. Follow that horizontal line to the extreme left, and you will recover the initial letter of the original message, namely: T. Da capo ad infinitum. Q. E. D."
Together we worked out the first line of the cypher in the leather-bound book. The complete layout ran as follows:
| W | O | N | F | O | R | T | O | F | O | R | A | T | E | W | O | N | F | O | R | T |
| Q | W | O | T | T | U | I | J | X | I | S | V | A | Z | P | I | H | N | X | J | X |
| T | H | A | N | E | C | O | U | R | T | A | U | G | U | S | T | T | H | I | R | D |
"And so on, world without end," commented Betty. "You can imagine how like mad I worked once we were on the train and rushing Southward. For now I knew why it was necessary to avoid entering that room, especially at this particular time of year."
The clocks were striking nine, and Chalmers wanted to drop in at "Powersthorp" on his way home. So he bade us good night, climbed into his car, and was off, the red star of his tail-light twinkling through the linden trees bordering upon the driveway. And I remained alone with Betty; only, for a long time, we did not speak; it was not necessary.