"Some one who knows the house," declared Adrian emphatically. "He
may have put on some masquerade costume just to frighten these
superstitious servants in case he was discovered."

"I believe Ad is right," agreed Donald. "What do you think,
Billie?"

"Maybe, Don; but I have a theory of my own. If I am right, I can
work it better if I tell no one."

At this moment the physician entered the room.

"How is Santiago?" asked Donald.

"Better! He has gone to sleep, and if he is not disturbed, I
expect him to be greatly improved when he awakens. I should not
be surprised if this were the turning point in his illness."

"Then we had all better go down on to the first floor and leave
him alone with his nurses."

"I'd give a good deal to know where Strong is," remarked Donald
as they were drinking their coffee an hour later.

"So would I," declared Billie. "I believe, if we can find him, we
can solve this entire mystery."

"As soon as we finish our coffee," suggested Donald, "let's get
busy and find him. He can't be far."

"That's right," said Adrian. "We'll round him up in short order.
Hey, Billie?"

"We ought to; but I'll tell you what. You fellows go out and see
if you can get a line on him, and I'll hang round the house to
see that the devil doesn't come and steal the rest of the house."

"Especially Lucia," laughed Donald.

"That's all right," was the good-natured reply; "but I have an
idea that the devil and Strong may have something in common."

"You don't think it was Strong who came and took the box, do
you?" queried Adrian.

"I don't know just what I do think, Ad; but I'm going to do a
little detective work and I want to give the impression that we
are all out. When you fellows go out, don't say anything that
would cause any one in hiding to think we are not all going out
together. Do you sabe?"

"Sure. I hope you'll get a clue if we do not."

When the others had gone, Billie sat quietly in his room for a
long time. He could easily have gone to sleep, as he had had only
a couple of hours' rest, but he made up his mind that he would
not be caught napping again if anything should happen.

But nothing happened.

The minutes passed into hours and it was rapidly nearing noon
when Billie made up his mind that it was a bad job.

"We had our chance at daylight," he muttered, "and now we will
not get another. Whoever is after the box, has it and is not
going to take any further chance of being caugh