“We’ve got quantities of keys to French ciphers, and numerous ones to the Blocked-Out Square, but they won’t translate this letter.” He took up a small book and opened it at a mark. “Here are samples of the latter: ecclesiastiques, coeur de roche, a deau eaux, fourreau, chateau d’eau, and so on. But, alas, none of them fits; the French Government has a new key. Indeed, she changes it every month or oftener; sometimes she changes it just for a single letter.”
“Then we must apply ourselves to obtaining the French key-word,” Harleston remarked. “Can you—do it?”
“Maybe we can pilfer it and maybe we can’t. At least we can make a brisk attempt. I will give orders at once. In the meantime, if you’ll keep me advised of what happens, we may be able to piece your and my information together and make a word.”
“I’ll do it!” Harleston replied and started toward the door. Half-way across the room he suddenly whirled around. “Lord, Carpenter. what an imbecile I am!” he exclaimed. “I fancy I’ve had the key-word all the while and never realized it.”
“There are too many petticoats in this case,” Carpenter shrugged.
“Never mind the petticoats!” Harleston laughed. “Get out the letter and try this phrase on it: à l’aube du jour.”
Without a word of comment, Carpenter set down the cipher message, letter by letter, and wrote over it à l’aube du jour. Then he took up a printed Blocked-Out Square and with incredible swiftness began to write the translation.
“Where did you get this ‘at the break of day,’ Harleston?” he asked as he wrote.
“Found it in Crenshaw’s pocket-book when he returned to hold me up,” Harleston replied.
“Only this isolated phrase?”