"These are the young gentlemen to whom I referred," explained the general, introducing the boys. "They are typical Americans and, being civilians and speaking Spanish fluently, will be just the ones to help you in your trouble." Then to the boys: "Don Esteban has a very delicate mission for which he asks the assistance of Americans. He wished me to detail three young officers for the work, but this I do not feel I can do, as it is strictly a private mission. If you feel that you can undertake it, he will be glad to explain it to you." "Anything that you recommend, General, we shall be glad to undertake," replied Donald, acting as spokesman for the trio. "Then I shall turn you over to Don Esteban, and as his business is pressing, I will excuse you if you wish to accompany him home." "A thousand thanks, General," said Don Esteban effusively. Then to the boys: "My automobile is at the door. If you will take seats in it, we shall be speedily at my house. You will pardon me if I speak nothing but Spanish, as I know very little English, although"--with an expressive glance at Gen. Funston--"I hope to know it better." Following Don Esteban, they were soon speeding through the streets and five minutes later entered a handsome patio. "This is my house," said Don Esteban. "Be pleased to consider it your own. Now, if you will follow me to the library, I will explain the mission I wish you to undertake." The boys followed without a word, but as they passed up the stairs Billie muttered under his breath: "Did you notice, boys, that this house backs right up against Santiago's?" CHAPTER XXIV. DON ESTEBAN'S STRANGE LOSS. "Before I explain to you the mission I wish you to undertake," said Don Esteban, "I must narrate briefly a story that has been handed down from the days of Montezuma. It is to the effect that when the Spanish conqueror, Cortez, was about to capture the City of Mexico, most of the treasure of the Aztecs was sunk in the lake, which at that time covered a portion of the Mexican plateau. "A part of this treasure is said to have been recovered, but the mine from which the gold of Montezuma was taken has never been discovered, although search has been made for upward of five hundred years. Some have supposed that the mine was adjacent to the City of Mexico and that it was flooded at the time the treasure was sunk in the lake. Others have thought it was located in the state of Michoacan, while still others have believed it located in the vicinity of Mt. Orizaba. "My reason for telling you this is that some years ago a strange appearing man came to our bank and made a large deposit of money, all in gold. He did not deposit it all at once, but brought it in a few thousand dollars at a time until it amounted to more than a million dollars. Then he disappeared and we have never seen him since." "And has he never called for any of the money?" asked Billie.