"That was part of one box which had survived the volcanic eruption which scattered Ulrich von Hagel's horde to the four winds. You remember that wisp of smoke we saw rising from the hillside in front of the great image? Well, I discovered that it came from a deep fissure in the mountainside at the foot of the idol. From the little cairn of stones, which still stands on the edge of the cliff, it was clear that the treasure had been stored in a cave which appears to have been hollowed out of the rock in front of the idol.
"Where that cave was is now a yawning hole belching forth smoke and streams of lava. In fact, as far as I can judge, the treasure was blown clean out of the mountainside. That this surmise is correct is shown, I think, by my discovery of the remains of a wooden box in which were still a few gold pieces. Other fragments of charred wood were scattered around. For the rest the treasure is gone and will never be recovered!"
Marjorie's eyes rested mournfully on my face; but I could not meet her gaze.
"But how did you discover all this?"
"The passage by which I escaped from the burial-chamber brought me out within a hundred yards of the image. The sulphur fumes from the fresh cone of the volcano caught me by the throat directly I emerged into the open. My one idea was to find you. So I crammed the gold pieces in my pocket and made for Horseshoe Bay to see if the yacht had returned. Finding no sign of her or you I started to reconnoitre. I guessed that Clubfoot and his party would be watching somewhere near the terraced rock and sure enough, as I was prowling in the undergrowth near here, I saw the whole gang file out towards the rock. I watched where they had come from and creeping up saw you and Grundt in conversation. The only thing that mattered then was to get you out of Grundt's clutches. I saw no signs of any guards but I made sure that Clubfoot would have help within easy reach. As I was turning things over in my mind I heard the Naomi's gun. So I decided to risk everything on a final bluff and I acted at once...."
"When they told me you were not in the cave," said Marjorie, "I couldn't believe my ears. How on earth did you manage to escape?"
"Well," I replied, "you remember that stone table on which the mummies lay? Under one of them I found, let in the table, a flat stone carved with a turtle. I don't know whether you realise the significance of that sign. The turtle was the mark of that celebrated buccaneer, Captain Roberts, who, in the old days, was a great man in these waters. The buccaneers are known to have used Cock Island for obtaining fresh meat and water—you can read about it in the 'Sailing Directions'—so the sign of the turtle set me thinking.
"I tried to get the stone up but it was firmly cemented in the table. However, in my pushing and thrusting I leant against the table edge and suddenly the whole top swung round outwards into the cave leaving a hole about five feet deep. The hole was the opening of a passage several hundred yards long which led into the open air——"
"But how did you manage to close the opening behind you?"
"Quite simply. I arranged the mummies as they were before, covering the turtle stone, then standing in the hole I drew the table-top back into place again. It is quite solid and does not ring hollow—the simplest and neatest device of its kind I ever saw. Roberts and his men must have used the burial-chamber for some sort of secret meetings, I imagine. Perhaps in their day Cock Island was inhabited...."