Then he realized his terrible situation. Somebody had uncovered the trap in the casemate and left it open, and he had fallen into the tank. He was down in that horrible, black, slimy pit. Perhaps he had struck his head in falling, but the water had broken the fall.
"Help! help!" he cried, when this dawned upon him. But he soon stopped that. All the men, he knew, were on the opposite side of the fort, and probably all in bed. There was not the faintest hope of making any one hear if he shouted all night. To climb out was impossible, for the hole was six feet above his head, in the middle of the ceiling. He was doomed to spend the night in that dreadful place, and in the morning he might hope to attract attention.
How long he stood there, shivering with the damp chill and with terror, he does not know. It was long enough, at any rate, to make him fear that he might lose his senses before morning, and fall and be drowned in the slimy black water. Perhaps older fellows than Frank would have shivered with fear in that awful black vault.
He had pulled himself together enough to try to dry his upper clothes, when he was startled by a slight noise overhead. Yes, he was sure he heard a noise; and the next moment he heard a voice. Ah! surely a human voice never sounded so sweet before! He had his mouth ready to cry out for help, when he caught a word or two that made him pause to listen.
"I tell you I'll wait no longer," the voice said. "They're all in bed before this, and we're going to work. Come on."
Frank was familiar with all the voices in the fort, but this was a strange voice. Evidently strangers had landed; but what could they mean by going to work at night?
He still waited to listen, but instead of more words he heard the tread of feet overhead. Could they be going away? Whoever the men were, he must have help, and he would have called out in a second more if-- Hark! There was a grating on the stones above, then a glimmer of light, as if from a lantern. Then another strange thing happened. By the dim light he saw the end of a ladder come down through the trap--not the trap over his head, but two casemates further down, nearer the sally-port.
By the same dim light Frank saw that the tanks were connected by broad brick arches, through which the water flowed from one to another. The ladder was let all the way down, and down it came four men, one after another, one carrying the lantern, all carrying hammers and saws, and all strangers. Frank was so surprised that he could do nothing but stand still and watch. There was no danger of his being seen, for he was in the deep gloom; but he could see every move the men made, as they carried the light.