"Two months after reaching the island, we sailed to the south, in order to explore the second island, noted on the chart, and it was then that the returning monsoon, which usually blows in the opposite direction from the one of six months before, wrecked the vessel, and the next day one of my companions and myself, who were so far as I then knew, the only survivors, reached the southern sh.o.r.e of an island, where we saw high mountains, so unlike those in the island where I was shipwrecked years before."

"While I think of it," remarked John, "how did you know about the second island, to which you refer?"

"I learned this from Walter."

"Then did you know anything about the skull on the headland, and the note which Walter left?"

"I knew about the skull, but never heard of the note to which you refer.

The discovery of the skull was an accident, and I attached no importance to it at the time. From the southern portion of the island we journeyed along the eastern coast, to the north, skirting a large forest on the way."

The boys looked at each other, significantly, but he did not notice this.

"Then we reached a large river, and to our surprise, found a boat, evidently of native manufacture, and with this floated down the stream to the sea."

"But where did you get the rope that we found in the boat?" asked George, eagerly.

He turned, and answered: "How did you know we put any rope on the boat?"

"Because that was the boat we made, and we found it afterwards, with the strange rope and oars."

"Strange oars. I know nothing about them. We used the oars found in the boat."

"Did you get the boat near a large falls?"

"Yes."

"And on the north side of the river?"

"Yes; but after we reached the sea, it was too rough, and the wind was blowing too heavily from the north to make it safe to navigate in that direction, so we went south, probably ten miles, and drew ash.o.r.e. The next morning when I awoke the boat and my companion were missing."

"Who was your companion?"

"Walter."

John looked indignant, and expressed his opinion very forcibly, but Clifford held up his hand, restrainingly. "Do not be too harsh. I have no ill will toward him. I did not know what to do, nor which way to turn, but went to the west, and before night, came, unexpectedly, on the remains of a fire, which led me to believe that I would find friends in the inhabitants.

"I went on and on, and caught up with the band, and was then horrified to find that they were having a feast, and sacrificing human beings. I saw Walter among the captives, but I could not contrive to let him know of my presence, and left the place as hurriedly as I could.

"After a month of struggling I reached the southern part of the island, and there, to my joy, found three of my companions on a life boat, belonging to a vessel called the _Investigator_, and together we made a course southeast, and there found the location of the second skull."

"But you knew nothing of that at the time, did you?"

"I did not know what the marks on the skull were for, but the finding of the second one was sufficient to revive in me the hope that, after all, the treasure might be found. One of the men, who was the intimate of Walter, figured out the course to be taken, and we reached the island to the north the second day.

"There, to our surprise, we found Walter, and he charged one of the men with me, with trying to secure the treasure, but I finally patched up the matter, and we agreed to work in concert. Then, when the next day, we found that Walter had lost the chart, we felt that it was a trick on his part to deceive us, and we separated. At that time I did not believe he told us the truth.

"Two days afterwards we pa.s.sed a party of natives, who were not aware of our presence, and then we saw that Walter, and the man with him, had been captured, and later believed that they had been killed. We searched the island, to find the cave, but were unsuccessful and thinking that an error might have been made, we concluded to sail for the island to the south.

"We found a tribe of natives when we landed, and owing to the exposure and the trials we had gone through I was taken ill, and grew worse and worse, and from that time on to the time I recovered two days ago, I had not the slightest idea of what pa.s.sed."

"When I spoke against Walter a few moments ago," said John, "you said he was not to blame. What did you mean by that?"

"During my wanderings, I found parts of the chart, which, I a.s.sumed, had been lost by John, and, probably, destroyed by the natives. The part I recovered was of no value to me, but it entirely changed my opinion of Walter."

But Clifford's story left something to be told. It did not explain why Walter tried to avoid meeting Clifford; or why he was so startled upon seeing the two skulls, or the reason for avoiding the reference to the letter to which his name was signed.

The boys were so intensely interested in his story that they did not notice the entrance of Blakely, who had brought Walter back, but when Clifford saw Blakely there was immediate recognition.

Clifford held out his hand to Walter, as he said: "I did wrong in doubting you. I understand from the statement made by Ta Babeda, that they found the chart the next day, after we met them, and that, of course, clears you."

"But I would like to know," said Harry, "what the other part of the inscription on the skulls means?"

"Do you refer to the sign of plus and the V?"

"Yes."

"When you went into the cave, where you found the copper box, how many chambers did you pa.s.s before coming to the large room?"

"I am not sure," he answered, "but I think four."

"Yes; and the case was found in the fifth chamber. The Plus sign indicated the cross-shaped cave, did it not?"

"Yes, and there are several other things which interest me," remarked George, gazing at John, as he continued: "Why should the inscriptions have been marked on the skulls?"

John slowly shook his head, as he looked at Clifford. The latter gazed vacantly into s.p.a.ce, as though reflecting, and finally said: "I do not know."

It will be remembered that when Walter entered the Professor's room, where Clifford was lying, he appeared to be startled at the sight of the skulls. The copper box which held one of them was in the adjoining room.

During the foregoing conversation Walter was mute, nor did he appear interested in the question propounded by George.

"It seems most curious to me that the skull taken from the copper box has the inscription on the right side, whereas the other one has them on the left side," observed Harry.

John and George saw the immediate change in Walter's face while Harry was speaking. His agitation was now plain to all, and the perspiration began to appear on his forehead.

John leaned forward as he said: "Do you know?"

Walter started at the vehemence of the question, and threw back his head, as he answered: "Did you find the copper box?"

"Yes," responded John, with a look of triumph.

Walter's features relaxed, and he seemed to sink down, as he gazed about him with a final look of despair.

"Then the quest is ended!" he muttered.

"What do you mean? Explain!" demanded John.

"When I began the search for the treasure of the caves, I was the owner of the original doc.u.ment written by Juan Guiterez before he died in the Spanish prison. Three attempts had been made to find the island, which contained the secret, and that secret was in the copper box which told of the places and the locations of the other caves. In each case the quest failed, and all perished. The peculiar significance arises from the fact that the only directions were given on a human skull by Guiterez himself, who declared that two of the skulls would have the inscriptions on the left side, while the one with the cryptic signs on the right side would be accompanied by the descriptions of the locations of all the Caves on the different islands."

"But why should there be three skulls?" asked George, in great eagerness.