"It must belong to the treasure box!" ejaculated Dick.
"Hurrah! We're gittin' closer to dat prize!" burst out Danny, and shook his bullet-like head enthusiastically.
All examined the key with interest. It was a little rusted at one end, but still good enough to use if the cedar box was brought to light, as Dick declared.
"We are on the right trail; I feel certain of it," said Menden. "For that old Spaniard mentioned a pile of bones to me."
"I wonder if Farvel has been here yet?" said Don.
"I think not—and I hope he doesn't come."
They moved on more slowly than ever. The foul air was now left behind and they gained a chamber where there was a steady current of cold air which made one and another shiver.
"What's that?" said Don, of a sudden.
He had heard a strange sound, and now they all noticed it.
"Is it somebody moaning?" gasped Leander.