They separated and searched the stockade from end to end. It was M'Wané who gained the first clue, who came running breathlessly to Crouch.
"Master," he cried, "the wood-stack has been moved."
Within the stockade they had noticed on their arrival a great quantity of firewood, which had been cut in the adjacent forest. On approaching this, Crouch saw at once that the wood-stack had been pulled down as if in haste. Calling out to Edward to bring the lantern, he awaited further developments. No sooner had Harden arrived than the mystery was solved.
Leading downward into the ground was a broad flight of steps. A kind of tunnel had been formed under the sand, about four feet wide and six feet high, revetted by wooden beams. So all the time Cæsar had been at liberty to escape, whenever he felt that he was sufficiently recovered of his wound to undertake the journey.
When Cæsar had constructed his stockade in the heart of the wilderness, he had been prepared for all eventualities and had neglected nothing. He had unlimited labour at his disposal. Knowing the nature of his business, and the hatred with which he was likely to be regarded by the neighbouring tribes, he had thought it likely that, at some future date, he might be called upon to undergo a siege. That siege might last for several months, by which time his provisions would be exhausted and he obliged to retreat. As far as they were able to discover, the subterranean passage had been made during the absence of de Costa on a two-months' journey to the Coast, in order to procure fresh supplies of dynamite. From the fact that the half-caste knew nothing whatsoever of the passage, it seems likely that the Portuguese had all along intended to desert his companion at the eleventh hour.
Without a word, Edward Harden descended the steps, holding the lantern on high to guide his friends who followed. The passage lay in a bee-line throughout the whole of its length. It was about three hundred yards long, and whilst it ran through the sandy sub-soil in the crater of Makanda, both its walls and roof consisted of solid logs. For the last hundred yards it pierced the living rock, and at last came forth in the impenetrable darkness of the forest.
By the aid of the lantern they were able to discover a path which led to the left, and after a few minutes' walking, this brought them to the river bank. Here, in the soft mud, was the indentation of the bows of a canoe. Moreover, the place was so screened by trees and tall reeds that no one, passing either up or down the river, would suspect for a moment that here was a mooring-place. It was here that the "phantom canoe" had lain, to be brought upstream by two or three of the Arabs from the stockade on the night of the attack.
No sooner did Crouch observe this evidence of the means Cæsar had taken to escape, than he shook his fist in the air.
"He's gone down-stream," he cried. "But, I'll follow him, if he leads me a ten-years' journey through the wilderness. I'll overtake that man, and I'll kill him. I swear it. I swear that I'll never set eyes upon the shores of England again, until I know that he is dead."
And that was the oath of Captain Crouch, which--when we have got to the end of the story--will prove to us that oaths are very futile after all. The strength of man is limited; in face of the wonders of the universe, his knowledge is indeed small. He may be strong and brave and unswerving of his purpose; but, after all, where men teem in cities, no less than in the heart of the illimitable and mighty forest, there is a greater Power than anything that is human--the all-pervading Spirit of the Universe, before whom the foolish vows of men are of infinitesimal account.