On the other side of the square they had heard Billie's shout, followed by the automatic, and had rushed to his aid.
In another minute both Strong and his hairy friend were overcome and securely bound.
"Where did you find him?" asked Donald, pointing to Strong.
"Down there," was Billie's reply, as he pointed toward the still open underground passage way.
"How did he get there?"
"I suppose he entered from a similar entrance in Don Esteban's patio. I have had an idea all the time that there was some reason for the position of these two houses."
"But it doesn't lead into the bank. How could he steal the box out of the vault?"
"There is the real thief!" exclaimed Billie, pointing to the ape. "He sneaked in while Strong kept the bank employés engaged. By some mistake in his understanding he put the envelope back in the bank the next day instead of putting back the box. It was he who crawled through the bars into Santiago's library. He was also the devil who scared the maid almost into fits."
"Well! Well!" exclaimed a voice from the gateway. "I never could have believed it."
The voice was that of Don Esteban, who had entered while Billie was speaking.