"One doesn't guess ciphers, they must be solved. And this one is of that peculiar kind that needs an arbitrary keyword for its solution, without the knowledge of which there is little hope of ever getting the answer."

"And you give it up?"

"Oh, no, indeed? I shall solve it, but we must find the word we need to make it clear."

CHAPTER XVII

THE CIPHER

"And how would the dime help, if we had it?" Iris pursued the subject.

"I'm not at all sure that it would," Stone replied, "but there must be some hint on it as to the keyword. I tried an ordinary dime, thinking the word we need might be 'Liberty' or 'United' or 'America,' But none of those would work. I tried to think out a way where the date on the dime would help----"

"But you don't know the date!"

"No; but I tried to find a way where a date would apply, but I can't think figures are needed, it's a _word_ we must have."

"Words on dimes are all alike," suggested Lucille.

"Yes, but suppose a word had been engraved on this particular dime as these letters are engraved on the pin."

"Aunt Ursula would have been quite capable of such a scheme," Iris averred, "for she had most ingenious notions about puzzles and ciphers.

Sometimes she would offer me a bill of large denomination, or a check for a goodly sum, if I could guess from the data she gave me what the figures were."

"And did you?"

"Never! I have no head for that sort of thing. It made my brain swim when she finally explained it to me."

"And yet I can't think the dime is necessary for the solution of this cryptogram," Stone went on, "or Young would have tried to get that also.

However, now we have the man himself, he must be _made_ to give up whatever knowledge he possesses."

"He won't," Iris said, positively.

Fibsy was poring over the string of letters, which he had copied from Stone's paper.

"That's so, F. S." he said, blinking thoughtfully, "there aren't enough duplicates of any letter to mean E. This is a square alphabet with a key word, sure."

"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

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z B C D E F G H I J K L M N O P Q R S T U V W X Y Z A C D E F G H I J K L M N O P Q R S T U V W X Y Z A B D E F G H I J K L M N O P Q R S T U V W X Y Z A B C E F G H I J K L M N O P Q R S T U V W X Y Z A B C D F G H I J K L M N O P Q R S T U V W X Y Z A B C D E G H I J K L M N O P Q R S T U V W X Y Z A B C D E F H I J K L M N O P Q R S T U V W X Y Z A B C D E F G I J K L M N O P Q R S T U V W X Y Z A B C D E F G H J K L M N O P Q R S T U V W X Y Z A B C D E F G H I K L M N O P Q R S T U V W X Y Z A B C D E F G H I J L M N O P Q R S T U V W X Y Z A B C D E F G H I J K M N O P Q R S T U V W X Y Z A B C D E F G H I J K L N O P Q R S T U V W X Y Z A B C D E F G H I J K L M O P Q R S T U V W X Y Z A B C D E F G H I J K L M N P Q R S T U V W X Y Z A B C D E F G H I J K L M N O Q R S T U V W X Y Z A B C D E F G H I J K L M N O P R S T U V W X Y Z A B C D E F G H I J K L M N O P Q S T U V W X Y Z A B C D E F G H I J K L M N O P Q R T U V W X Y Z A B C D E F G H I J K L M N O P Q R S U V W X Y Z A B C D E F G H I J K L M N O P Q R S T V W X Y Z A B C D E F G H I J K L M N O P Q R S T U W X Y Z A B C D E F G H I J K L M N O P Q R S T U V X Y Z A B C D E F G H I J K L M N O P Q R S T U V W Y Z A B C D E F G H I J K L M N O P Q R S T U V W X Z A B C D E F G H I J K L M N O P Q R S T U V W X Y A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

"The way to use this," he explained, "is to take a keyword--let us say, Darrel. Then let us suppose this message reads, 'The jewels are hidden in ----.' Of course, I'm only supposing this to show you our difficulties. I write the message and place the code word, or keyword above it, thus:

"Dar relDar rel Darrel Da The jewels are hidden in

"we repeat the keyword over and over as may be necessary. Then we take the first letter, D, and find it in the line across the top of our alphabet square, and the letter under D, which is T we find in the left hand perpendicular line. Now trace the D line down, and the T line across, until the two meet, which gives us W. This would be the first letter of the cipher message if the key word were Darrel, and the message like our suggested one. But the first letter of the cipher we have to solve is O, and no possible amount of guessing can go any further unless we have the key word Mrs. Pell used to guide us. See?"

"Yes, I see," and Miss Darrel nodded her head. "It's most interesting.

But, as the first letter of the cipher is O, why can't you find O in your alphabet and go ahead?"

"Because there are twenty-six O's in the square, and it needs the key word to tell which of the twenty-six we want."

"It's perplexing, but I see the plan," and Lucille studied the paper, "however, I doubt if I could make it out, even if I had the word."

"Oh, yes, you could, and if we get the dime and the receipt that was in the pocket-book we can try every word on them both, and I feel sure we'll get the answer. Now, since Pollock, or Young, rather, was so desirous of getting the pin, I argue that he had the necessary key word.

Therefore we must get it from him, if we can't get it ourselves, and I doubt if he'll give it up willingly."

"Of course he has the key word," Iris said, "for he told me he could find the jewels and no one else could, if I'd hand over the pin. And he offered to go halves with me! The idea!"

"And yet, if he has the key word, and won't give it up, you can never find the jewels," observed Stone.

"You don't advise me to accept his offer, do you?"

"No; Miss Clyde, I certainly do not. But there is another phase of this matter, you know. If Charlie Young stole that paper from the pocket-book he was the one who attacked your aunt----"

"And Winston Bannard is in jail in his place! Oh, Mr. Stone, let the jewels be a secondary consideration, get Win freed and Charles Young accused of the murder--he must be the guilty man!"

"It looks that way," Stone mused; "and yet, Bannard admits he was here that Sunday morning, and had an interview with his aunt. May he not have obtained possession of the receipt--oh, don't look like that! Perhaps his aunt gave it to him willingly, perhaps she told him of its value----"

"Oh, no," cried Iris, "if all that had happened, Win would have told me.

No; when he discovered that the receipt was left to him and was especially referred to in the will, he was amazed and disappointed to find that old pocket-book empty."

"He seemed to be," said Stone, but his manner gave no hint of accusation of Bannard's insincerity.

"Mr. Bannard, he ain't the murderer," declared Fibsy; "and that Young, he ain't neither. Because--how'd they get out?"

"How did the murderer get out, whoever he was?" countered Stone.