"All your ideas are theoretical," said Ezra drily. "Perhaps Caprice never stole her own jewels, or sold them to my father." "Yes, she did, I'll swear," retorted Naball decisively. "Why wouldn't she prosecute? why did I find Villiers with one of the jewels? You bet, she stole them for some freak, and I daresay Villiers committed the murder to get them back." "I don't think my father would have kept such valuable jewels as that about the premises." "No; he'd put 'em in the bank." "No, he wouldn't," retorted Ezra; "he sent all his jewels to Amsterdam. And here," holding up a letter, "is an envelope with the Dutch postmark." "By Jove!" ejaculated Naball, under his breath, "what a queer thing if it should turn out to be those diamonds of Caprice's. Open the letter." "Suppose it does turn out to be the diamonds," said Ezra, slowly tearing the envelope. "Well"--Naball drew a long breath--"it will be the beginning of the end." "I hope it will end in Keith's being released," said Eugénie, looking at Ezra with intense anxiety. That gentleman took out the letter, and glancing at it for a moment, gave vent to an ejaculation of disgust. "What's the matter?" asked Eugénie and Naball together. "The letter is in cypher," said Lazarus, tossing it over to the detective. "I don't think we'll be able to read it." "Oh, we'll have a try," said Naball, quickly spreading oat the letter. "Let's have a look at it." The letter was as follows:-- "Dsidanmo seaf utnes teh ssteon ryiks sgenlil gto teher tdhnoaus sgennid it lses teher hduenrd bneiertns." "What the deuce does it mean?" asked Naball in a puzzled tone. "It's a cypher, evidently, of which my father alone possesses the key," said Ezra. "I'll have a look among his papers, and if I find it, it will soon make sense of this jumble of words." "It's like a Chinese puzzle," observed Naball, glancing at it. "I never could find out these things." "Let me look," said Eugénie, taking the letter. "I used to be rather good at puzzles." "We'll find this one out," said Naball significantly, "and you'll do some good for Stewart." "You think it's about Caprice's diamonds?" she asked. "I think it's about Caprice's diamonds," he replied. "I think the words have been written backwards," said Ezra, looking over her shoulder. Eugénie shook her head. "I don't think so," she replied, scanning the letter closely. "If so, the word 'it' would have been written 'ti.'" "Try a word of three letters, if there's one," suggested Naball, "and you can see how the letters are placed." "Here's one spelt 'g-t-o.' What word can be made out of that." "Got," said Ezra eagerly. "Well, if so, in the cypher it reads, the first letter 'g,' the last, letter 't,' and the middle letter at the end." "What do you think of that?" asked Naball bluntly. "That the sender of this has taken the first and last letters of a word, and written them in rotation." "I don't understand," said Naball in a puzzled tone.