"Aunt Ursula was crazy over ciphers!" exclaimed Iris, "she was always making them up. But she always called them ciphers, never cryptograms, or perhaps I might have thought that crypt. was an abbreviation. But can't you guess it, Mr. Stone?" "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!"