ph of Madeline Spencer, a well-known German Secret Agent in
Paris," Carpenter remarked slowly; "and the letter is borne by Madame
Durrand to the French Ambassador. You see, my intuition was right? the
letter is in French; and as it is of French authorship the key-word is
French. That narrows very materially our search. Find the key-word to
the Vigenerie cipher of the French Diplomatic Service and we shall have
the translation."

"You haven't that word?" Harleston asked.

"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: _a l'aube du jour_."

Without a word of comment, Carpenter set down the cipher message, letter
by letter, and wrote over it _a 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?"

"Yes--and signed with the single initial 'M.'"

"Hump!" Carpenter commented. "Mrs. Spencer's name, I believe you said,
is Madeline. I tell you there are too many women in this affair."

Suddenly he threw down the pen. "What's the use in going on with it. If
you can supply a key to this key we may