Lucia made a little grimace.
"I'm nearly seventeen," she said.
"Botheration!" said Billie. "We are not here to discuss ages, but to find out how this box came here. I have no doubt that Lucia has seen many similar boxes in her time."
"Well," asked Donald, somewhat nettled, "what do you propose to do?"
"In the first place, I want to search the house."
"That's a good idea," declared Adrian. "Donna Lucia, will you lead the way?"
"Certainly. Right this way; but don't go into father's room. I know there is no one in there. One of the servants has been with him every minute of the time."
Headed by Lucia, the boys explored the house from top to bottom, but not a sign of any one could they find. So far as they could determine, the box must have come in of its own self.
"I'll tell you one thing we can and must do," said Billie, after they had returned to the library. "We must keep a watch in this room to-night. Whoever put the box here may return."
"Right!" from Don. "You do have occasional lucid intervals, Billie."