“And get shot down,” interrupted Dick.  “No, I think the ghosts idea is as good as anything.  Quick, take off your coats and tie your handkerchiefs over your faces.”

The boys had on light colored outing shirts, and these, with the handkerchiefs over their faces, made them look quite ghostlike in the gloom under the trees.

“Now, when the time comes groan,” said Tom “Ghosts always groan, you know.”

“And let us order them back,” added Sam.

“But be sure to do it in very ghostlike tones,” warned Dick.  “If our voices sound a bit natural they’ll get suspicious at once.  If they come for us, or shoot at us, drop behind the rocks and run into the woods.”

It must be confessed that the boys were doubtful of the success of their ruse.  Yet they felt they must do something to hold the treasure seeking party in check, at least until morning.  With the coming of daylight they could signal to the Rainbow and with the aid of those on the steam yacht probably rout the enemy.

The Rover boys advanced along the trail until they reached a spot they deemed favorable for their purpose.  Then Dick gave his brothers a few more directions.

Presently they saw the rays of the gas lamp and the lantern in the distance.  At once Tom set up a deep groaning and Sam and Dick joined in.

“What’s that?” asked Shelley, who was the first to hear the sounds.

“Sounds like somebody in distress,” answered Sid Merrick.

“Thought you said there was nobody on this island?” came from Cuffer.

“Didn’t think there was.  Maybe it’s some native who—­”

“Look! look!” screamed Tad Sobber and pointed ahead with his hand.  “What’s that?”

“What’s what?” asked the men in concert.

“There—­that thing bobbing up and down over the rocks?” And Tad Sobber trembled as he spoke.  This lonely walk through the darkness of the forest had somewhat unnerved him.

“That’s strange,” muttered Merrick.  “It’s groaning!”

“It’s a ghost!” screamed Tad, and shrank back, as did Cuffer and Shelley.

“A ghost?” repeated Sid Merrick.  “Nonsense!  There are no such things as ghosts.”

“It cer-certainly looks like a-a ghost!” faltered Cuffer.

“It is a ghost!” said Tad, his teeth beginning to chatter.  “I-I ca-can hear it gro-groan!  Come on ba-ba-back!” And he began to retreat.

“Back with you!” came in solemn tones.  “Back with you!”

“No white man must come here,” said a second voice.  “This is sacred ground!”

“He who sets foot here dies!” came from a third voice.  “This is the burial place of the great Hupa hupa!  Back, if you value your life!” And then followed a jabbering nobody could understand, and white arms were waved wildly in the air.

This warning was too much for Tad Sobber, and without further ado he took to his heels and retreated down the trail whence he had come.  Cuffer followed him, and Shelley also retreated several yards.