"Awake, my son," were the words he heard. "It is now time that I reveal to you the secret of my life. It is now time that I should tell you the secret of the treasure of Montezuma."

"That's right, Prince," said Billie sleepily. "Let her go."

Santiago regarded him interrogatively.

"What said my son?"

"Oh, yes, Prince. I forgot you only understood good English. Let her go, means proceed with the secret."

"Let her go. Let her go," Santiago repeated a couple of times.

"Yes," he continued, "I had forgotten about her."

He clapped his hands and the same servant who had first appeared approached his chair.

Santiago gave an order in a language which Billie did not understand, but which he imagined was Indian, and the servant withdrew, only to reappear a few minutes later with a young woman who greatly resembled Santiago and who was also arrayed in a gorgeous costume.

She had evidently not expected to meet a stranger, for she drew back upon seeing Billie and the color rushed to her face.

"Come hither, daughter," was Santiago's command.

The young woman obeyed.

"Lucia," said Santiago, "this is the honorable young man whom I have chosen for my heir. Henceforth consider him your betrothed.

The marriage shall take place one new moon from to-day."

"Oh, Father," cried the girl, her face becoming even more scarlet than before, "I cannot----"

"No!" interrupted Billie, springing to his feet, "neither can I.

You ought to be ashamed of yourself, Santiago----"

"What!" cried Santiago, springing to his feet and again drawing his sword. "Who calls me Santiago? I am Prince Ixtazhl of the great Aztec nation and guardian of the treasure of Montezuma!"

He raised his sword and would have stricken Billie down ere the boy could have prevented had not the young woman thrown herself between them and seized his arm.

At the same instant the door from the ante-room opened and Donald and Adrian entered.

CHAPTER XVIII.

A MISSION FOR FUNSTON.

"Santiago!" exclaimed Donald.

"By all that's great!" from Adrian.

"Help!" cried Lucia. "He will do something desperate!"

Donald and Adrian sprang forward, but their a.s.sistance was not needed. Billie had by this time gathered his wits and in a twinkling the mad-man was disarmed.

"Shall we bind him?" asked Adrian as they came forward.

"No, indeed," replied Billie as the now helpless man sank down upon the chair. "He isn't dangerous."

"What's it all about?" queried Donald.

"Oh, nothing much! He simply wanted to make me his heir and marry me to his daughter."

Donald and Adrian cast an admiring gaze upon Lucia, who was now kneeling at her father's side.

"Well," said Adrian in an aside, "I don't see why you should object to that."

"Who said I objected?" demanded Billie. "It is the young woman who objects."

"But whoever supposed he had a daughter?" said Donald.

"Not I," from Billie. "But this is certainly a queer mess."

Then to Lucia: "How long has he been in this way, Senorita?"

"Only a few days. Since this trouble with the Americanos."

"But how could that affect him?"

"It is a long story, senor. For years he has been trying to overthrow the government. When Madero was made president, he was happy. Then came that awful tragedy, by which Madero was killed.

Since that time he has not been himself. But when it became evident that the United States would interfere he became as you have seen him to-day."

"When I told him that all the United States wanted was to get rid of Huerta, he was much pleased," explained Billie. "That was when he proposed to make me his heir."

Lucia's cheeks grew red, as she asked: "And did you accept his proposal?"

"I neither accepted nor rejected. I just followed him in to see what would happen next."

"But would you accept?" insisted Lucia.

"That depends," replied Billie, with a touch of color in his own face. "But what had we better do now? You and I will discuss the other question later."

"The best thing we can do," interposed Donald, "is to report to Lieutenant Blunt. Isn't there some place, Senorita, where your father can be placed for safe-keeping?"

"He will be perfectly safe here with me, senors, if the servants are allowed to remain."

"They certainly will be," declared Billie. "I will personally vouch for that. We have done Captain Rush a good turn to-day and I know he will be glad to do that much for us. And besides, the Americans will harm no one."

Lucia gave Billie a grateful look as she replied:

"Ah, senor, I shall trust it all to you. I can see that you are a friend of my father and I know you are telling the truth."