But it was already as strong as it could be made; and when he was satisfied on that point, he took stock of his ammunition, and made a fresh noose for the lasso which Hal had cut. Just as he had finished a beautiful slip knot, his ear was caught by a low whistle. Ducking to avoid the shot for which it might be the signal, he listened again. No shot followed; the whistle was twice repeated.
Standing upright again, the boy glanced hastily round. He fancied that the whistle came from the direction of the stream. He was still wondering what it meant, when another whistle, another, and yet another, and all from different directions, echoed round the fort. Each, like the first, was repeated twice, but yet nothing happened.
He strained his eyes this way and that, and then suddenly fitted a couple of bullets into his catapult, and fired into some bushes on the left. A sharp but quickly-suppressed squeal of pain was the result. Again and again he fired, but only to be met by a heroic silence. Either his shots missed or his victim refused to cry out.
Suddenly Hal's voice rang out.
"One!" he shouted.
There was a pause.
"Good," thought the boy. "At three the fun begins. Kind of them to give me warning."
Confident that he would have a few moments' breathing space, his watchful vigilance relaxed. Instead of keeping a sharp lookout, he ran his eye once more over his defences, and was considering whether it would be better to use the shorter or the longer lasso, when Hal's voice made itself heard again.
"Two!" he shouted with the full force of his lungs, and simultaneously a wild war-whoop went up from his army. There was the sound of breaking branches, and from different quarters of the wood four of the besiegers broke into the open and advanced at the double.
This movement was the outcome of a deeply-laid plan of Hal's. He knew that if an advance was made at the word "two" the fort would be taken completely by surprise, and under cover of the attack from the front he was, in the meantime, bringing the heavy gun—the water-barrel—into position at the rear.