himself among your men."

"Oh, he was an American, was he?" laughed Donald. "Then I believe
we can put our finger on him with ease. But the man we have in
mind always carried with him an ape."

"Then it may not be the same," replied Don Esteban, "for this one
had no ape with him either time."

"It certainly does look like a mystery," was Adrian's comment.
"Where is the vault from which the box was taken?"

"On the other side of the patio."

"May we examine it?"

"Certainly. I'll show it to you now."

Don Esteban led the way downstairs and across the patio. Opening
the rear door of the bank, he escorted them within and closed the
door.

Passing behind the counter, he opened the iron door of the vault,
disclosing within a good-sized chamber, in the rear of which was
set the great steel safe, locked with a time lock.

"There," explained Don Esteban, pointing to an upper shelf, "is
where the box stood."

"Oh, it was not a large box, then!" said Adrian.

"Oh, no! Not more than eight or nine inches cube."

The boy examined the vault carefully by the light of a gas jet.

"There seems no way that any one could have entered except by the
door," said Donald.

"None whatever!"

"You are sure there is no opening in the ceiling?"

"Absolutely."

Don Esteban led the boys out and locked the door of the vault.

"Well," declared Donald as they came out into the patio after
finishing their inspection, not only of the vault but of the rest
of the office, "I guess we had better go home and study over the
matter a little. I should not be surprised if we could put our
hands upon the mountebank with very little trouble; but I feel
sure he had nothing to do with the disappearance of the box."

"I wish I could feel that way," said Adrian after they were out
of hearing of Don Esteban. "I have never quite trusted Strong.
There is something strange about him."

"Yes, he is a bit queer; but how on earth could he have stolen
the box if he did not even go behind the counter?"

"He couldn't; but still I mistrust him."

"I wonder where Ambrosio was all this time?" mused Billie.

"Tied up at home, most likely. An American among Americans would
hardly feel like traveling around with a hand organ and a
monkey," was Don's emphatic reply.

Upon arriving at Santiago's residence they were told that
Strong had been there earlier in the evening and seemed much
disappointed at not finding them at home.

"Did he leave any word?