An instant later the opening was closed and Billie was left in the darkness, except for the light of his torch.
CHAPTER XXIX.
THE MYSTERY DEEPENS.
While Billie was making his discoveries Donald and Adrian had also been busy.
When they left the house, at Donald's suggestion, they went first to the bank and told Don Esteban about the disappearance of the box and what the maid had seen. He was much disappointed until it was explained to him that they also had another clue.
"We shall spend our time in the slums," said Donald, "while our chum keeps watch at the house. We feel sure that between us we shall solve the mystery."
"I hope so," was Don Esteban's response. "Do you think I might be able to see this man Santiago?"
"I'm afraid not, sir! The doctor wants him to sleep as long as he can. We will let you know later in the day."
Leaving Don Esteban, the boys started for the plaza, intending to play the part of sightseers and visit every place in which a mountebank might reasonably expect to go. They felt certain that Strong would keep away from the more aristocratic places.