eard. "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 assistance 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