"That's right," agreed Innis.
"But they'll never think of taking an old advertisement envelope, that looks as though it was just stuck away behind the mirror and forgotten," went on Paul.
"You're right—we'll fool 'em!" cried Dick, and at the next stopping place this simple trick was carried out.
CHAPTER XX DOWN HILL
"You'd never suspect it was there; would you?"
"Not at first glance."
"And unless we meet with some one who was as clever as the amateur detective that Poe tells about, who looked in the simplest place for the letter instead of in the hardest, we'll be safe," said Paul.