"Better not give me a chance," was the grumbling reply, as the trooper bit off a big piece of tobacco and tucked it away in his cheek.

Reveille was just sounding when the boys, accompanied by their three friends and Ambrosio, perched upon Billie's horse, drew up in front of Lieut. Grant's quarters. They had been recognized and pa.s.sed through the lines, and as the men caught sight of them they were given a hearty cheer.

"You seem to have made friends," laughed the lieutenant as he greeted them, "and there is every reason why you should. The general will be glad to see you and hear your report. I have no doubt you have a good story to tell, and he likes a good story."

When the boys reached home they found the gate still locked, although it was now considerably past the time when the household was astir. Their knock was answered by the _portero_, who, in response to a question by Billie, said that Santiago was seriously ill and had been for thirty-six hours.

"What is the matter?" asked Donald.

"Fever."

"I am not surprised," declared Adrian. "The strange thoughts he has been thinking so many days were bound to result in something serious."

"Perhaps it is not convenient for us to remain here," said Mr.

Black. "We can, I am sure, find some other place."

But at this moment Lucia appeared at the head of the stairs.

When made acquainted with Mr. Black's words she would not hear of his taking Josie to any other house and gave orders for making her perfectly at home. The only one who did not remain was Strong.

"I'll come back this evening," he said. "I have a strange story to tell you boys and I may need your help in locating a man I am most anxious to find."

But he did not come back that evening, and when he did come the next night the boys were not there, having been invited to dine with Gen. Funston. Had things not happened thus, a part of this story could never have been written, for it was while dining with the general that the boys were given a duty to perform, which was the most arduous of all their adventures in the land of the Montezumas.

And this was the manner of it.

They were just finishing dinner and Billie was congratulating himself that he had had his fill of good American cooking, when an aide announced that a Mexican gentleman, Don Esteban Mendoza, craved an immediate audience with Gen. Funston.

"I am sure you young gentlemen will excuse me a few minutes,"

said the general, "as Don Esteban is one of the prominent bankers of the city and I know his business must be of importance."

The boys were glad to accept the proffered excuse and the general withdrew, leaving them in the company of several members of his staff, to whom they briefly related their recent adventure. When they told of the "ambush" there was much amus.e.m.e.nt.

In the midst of their conversation the general returned accompanied by Don Esteban.

"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 a.s.sistance 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 pa.s.sed 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.

"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 bra.s.s-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?"