"Good for you, Terence!" and Stone smiled approvingly. "You're a real genius for ciphers! Now, where's the key word to be looked for?"

"On that paper Mrs. Pell left to Mr. Bannard," and Fibsy's eyes sparkled at the idea that suddenly sprang to his brain. "Why, of course, Mr. Stone! I didn't know I was going to say that, till it just came of itself. But, don't you see? She left the pin to Miss Clyde, and the receipt to Mr. Bannard and it takes them both to solve the cipher!"

"And that receipt was stolen by the man who murdered Ursula Pell!" said Miss Darrel; "he must have known its value!"

"It may be you've had an inspiration, Fibsy," conceded Stone, "and it may be the word is not on that receipt after all. But we must use every effort to get the paper and, also, to find that dime. It may well be a word is engraved on the coin, in the same microscopic letters as these on the pinhead. We must try both means of solution. Will you hunt the dime, Fibs?"

"Sure, but I'll bet the word is on the paper. Else why'd the old lady say that Mr. Bannard would find that receipt of interest to him? And, too, as she left the jewels to two heirs, fifty-fifty, it stands to reason part of the means of finding them should be given to each party."

"That's mere conjecture," Stone said, "but we'll look up both. I've worked hours over the cipher, and I've proved to my own satisfaction that it cannot be solved without the knowledge of the one word needed. It's like the combination of a safe, you have to know the word or you can never open the door."

"Tell me a little about it, just what you mean by key word," begged Lucille, "I know nothing of ciphers."

"I make it out that this cryptogram is built on what we call the Confederacy Cipher," Stone informed her. "It is a well known plan and is much used by our own government and by others. It is the safest sort of a cipher if the key word is carefully guarded. To make it clear to you, I will put on this paper the alphabet block."

Stone took a large sheet of paper, and wrote the alphabet straight across its top. He then wrote the alphabet straight down the left hand side. He then filled in the letters in their correct rotation until he had this result

ABCDEFGHIJKLMNOPQRSTUVWXYZ
BCDEFGHIJKLMNOPQRSTUVWXYZA
CDEFGHIJKLMNOPQRSTUVWXYZAB
DEFGHIJKLMNOPQRSTUVWXYZABC
EFGHIJKLMNOPQRSTUVWXYZABCD
FGHIJKLMNOPQRSTUVWXYZABCDE
GHIJKLMNOPQRSTUVWXYZABCDEF
HIJKLMNOPQRSTUVWXYZABCDEFG
IJKLMNOPQRSTUVWXYZABCDEFGH
JKLMNOPQRSTUVWXYZABCDEFGHI
KLMNOPQRSTUVWXYZABCDEFGHIJ
LMNOPQRSTUVWXYZABCDEFGHIJK
MNOPQRSTUVWXYZABCDEFGHIJKL
NOPQRSTUVWXYZABCDEFGHIJKLM
OPQRSTUVWXYZABCDEFGHIJKLMN
PQRSTUVWXYZABCDEFGHIJKLMNO
QRSTUVWXYZABCDEFGHIJKLMNOP
RSTUVWXYZABCDEFGHIJKLMNOPQ
STUVWXYZABCDEFGHIJKLMNOPQR
TUVWXYZABCDEFGHIJKLMNOPQRS
UVWXYZABCDEFGHIJKLMNOPQRST
VWXYZABCDEFGHIJKLMNOPQRSTU
WXYZABCDEFGHIJKLMNOPQRSTUV
XYZABCDEFGHIJKLMNOPQRSTUVW
YZABCDEFGHIJKLMNOPQRSTUVWX
ZABCDEFGHIJKLMNOPQRSTUVWXY
ABCDEFGHIJKLMNOPQRSTUVWXYZ