“Unless we hit on it by a lucky accident. That is why the keyword cipher is practically insoluble without knowledge of the keyword. It is not even necessary to have a word. A prearranged code of letters will do, known only to the composer of the cryptogram. If he wanted anybody else to decipher his cryptogram, he would have to divulge to him not only the form of table he worked on but the code of letters forming the keyword.”
“Well, I do not see we are much further forward,” said Marsland despondently. “Of course, it’s very clever of you to have found out what you have, but we are helpless without the keyword. The old man is not likely to have divulged it to anybody.”
“You are wrong,” said Crewe. “He has divulged it.”
“To whom?”
“To this paper. As I said before, he did not want his cryptogram to be insoluble; he wanted his heirs to have his money, but he did not want it found very easily. You have forgotten the texts at the bottom of the paper. They have not been placed there for nothing. The keyword is hidden in them.”
“I forgot all about the texts—I was so interested in your reconstruction of the cryptogram,” said Marsland. “As you say, he didn’t put the texts there for nothing, so it seems likely that he has hidden the keyword in them. But even now we may have some difficulty in finding it. Do you propose to take the texts word for word, testing each with the table, till you find the right one?”
“That would take a long while,” said Crewe. “I hope to simplify the process considerably. In fact, I think I have already discovered the keyword.”
“You have!” exclaimed Marsland, in astonishment. “How have you managed that?”
“By deduction from the facts in front of us—or perhaps I should say by reflecting on the hints placed in the texts. Isn’t there something about those texts that strikes you as peculiar?”
Marsland examined them attentively for some time, and shook his head.