"Not in person, although he has drawn upon it at frequent intervals. The name under which it was deposited is James Moon." "An American?" asked Donald. "I could not say whether he was an American or an Englishman. We took him for the latter. But now I am coming to the real part of the story. "In addition to the money which he deposited, he also left with us a small brass-bound box, in which he said there were valuable papers. He gave orders that it should be delivered to no one but himself in person, or until the expiration of ten years. The ten years will be up in a few days and this afternoon I bethought me of the box. But when I went into the vault in which it has been kept for so many years, the place upon an upper shelf, where it has always stood, was vacant. The box was gone!" "Gone?" exclaimed all the boys in unison. "Do you mean stolen?" "So it would appear." "How could it have been done?" asked Adrian. "I cannot say; but the strange thing about the whole matter is that in place of the box, there lay upon the shelf an envelope--yellow with age, upon which was written in ink that had scarcely faded the words: 'Montezuma's Mine.'" "Well, what do you think of that?" queried Billie, looking at the others in amazement. "I don't think," laughed Adrian. "It's up to you to do the thinking." "Is there no clue whatever?" asked Donald. "Not that could be really called a clue. The only suspicious thing that has happened to-day at all, was that a mountebank came into our bank----" "A mountebank!" from all. "Yes." "Did he have an ape with him?" "No! He was quite alone. He did not come in to make merry, but to get a bill changed. While he was there he was observed to scrutinize the place very closely." "But he did not go into your vault?" "No! He took his change and went peaceably out." "Then, why should you suspect him?" insisted Donald, casting a knowing glance at the other boys. "Because, an hour later, he came in again and said that one of the bills we gave him as change was a counterfeit." "Was it?" "No, it was not, although it was an old issue. The teller who waited upon him had no recollection of ever having seen the bill before, but rather than have a scene, we gave him another bill for it." "How large a bill was it?" asked Adrian. "Only a peso"--that is a dollar--"and it seemed hardly worth talking about; but you'd have thought it was a hundred." "Perhaps it seemed a large amount to him," ventured Billie. "Perhaps," admitted Don Esteban. "But be that as it may, I should like to see the man again, and especially would I like to know where he got that old dollar." "Why?" "Because it may have come out of that box." "Well, yes," said Donald, with a shake of his head, "it might have; but how could the mountebank have gotten the box?" "That is the mystery," was Don Esteban's reply. "And how do you wish us to help you?" asked Adrian.