“Let’s call for them,” suggested Songbird, and this was done, but no reply came back.

“They have started on the hunt for the cave, just as I supposed they would,” said Mr. Rover.

“Den let us git aftah dem directly,” said Aleck.  “I feels like I could tramp all night widout half tryin’!”

Tying up the rowboat, and shouldering their tools and provisions, they set off along the shore of Horseshoe Bay, just as the three Rover boys had done.  Bahama Bill led the way, with Mr. Rover beside him, carrying the electric light, which gave out fully as much light as did the acetylene gas lamp carried by Merrick.

“Here are some footprints!” cried Mr. Rover, after a short distance had been covered.

“Dem was made by our boys!” cried Aleck, after a minute examination.  “I know dem shoes, fo’ I has shined ’em many de time!”

“If they walked in that direction they took the wrong course,” was Bahama Bill’s comment.  “Like as not they got turned around among the trees an’ in the dark.”

“We must locate the party with that strong light we saw from the yacht,” said Mr. Rover.  “Perhaps in doing that we’ll come up to my sons.”

Once on shore, the old tar said he remembered the locality well, and he did not hesitate in pushing forward, across the path taken by the three Rover boys, and then to a trail which the Rovers had missed.  They had to climb a small hill, and here it was that Bahama Bill showed the first signs of perplexity.

“Queer!” he muttered, coming to a halt and gazing around.  “Mighty queer!”

“What is queer?” questioned Anderson Rover.

“This looks changed to me.  When I was here afore there was a rock yonder, an’ the crowd placed a mark on it fer a guide as I told ye.  Ain’t no rock there now!” And he scratched his head as if he was afraid he was not seeing aright.

“When you were here was a good many years ago,” said Songbird.  “The rock may have tumbled down the hill.  Let us look around.”

This advice was followed, and after a long hunt a rock was found in a hollow.  It had a peculiar mark cut upon it.

“That’s it!” cried Bahama Bill, in delight.  “I knew it must be around here somewhere—­but what made that big rock tumble down?”

“Maybe somepody pushed him ofer,” said Hans.

“Four men couldn’t budge that rock,” declared Fred.

“I believe an earthquake must have done it,” came from Anderson Rover, and suddenly his face grew grave.  “I trust no earthquake has disturbed the treasure cave,” he added.

They pushed on, but scarcely had they covered a quarter of a mile when Bahama Bill called another halt.  And well he might, for the trail they had been following came to an abrupt end in front of a pit several rods in diameter and twenty to thirty feet deep.  The bottom of the pit was choked up with rocks, dead trees and brushwood.

“What now?” asked Mr. Rover, and his tone betrayed his uneasiness.