It was with a feeling of intense relief that the boy woke at last in the faint dawn of morning, sprang from the bed, and rushed to the open window again, to thrust his burning brow out into the cool, fresh air. The beating in his brain was gone, his mind was clear, and he strained out to try whether he could hear through the roar of falling waters the hammering that had tormented him all through the night. "No," he said, "it's impossible to hear it from this window;" and he hurriedly dressed, to make his way out and up to the spot where he had stood with his friends. "Nothing now," he said. "Could it have been fancy?" He listened for a few minutes longer, and then mounted the rough steps, to stand on the top of the great stone wall to listen from there once more, before gazing up the valley and noticing that there were two little clusters of wild-ducks busily feeding just at the mouth of the stream where it entered the pool. There was a faint glow in the east, and flecks of gold high towards the zenith, promises of a glorious day, and he turned slowly, hesitating as to whether he should go back to bed. "No! Rubbish!" he said. "I'll go and rouse up old Josh. Yes, and wake up Mr Manners, too. He'd like to see this glorious sky--ah! what's that?" That was something unusual which had just caught his eye, for as he spoke he turned to look right along the top of the dam, where he seemed to see a strange disturbance on the surface of the water just at the end where the wall joined the rugged cliff. "It must be a great trout," he said, "one that's being beaten against the stones, and is half-dead. No; I believe it's an otter." He ran along the top of the wall and looked down in wonder, to see that a strange whirlpool seemed to have been formed, where twigs of dead wood, bits of grass, and autumn leaves were sailing round and round, before being sucked down a central hole. "What does that mean?" he thought; but he acted as well as thought, going quite to the edge of the wall, and then descending the steep built-up slope of stones and cemented earth, to where at the base of the dam-wall he found himself face to face with a sight so suggestive of peril that he turned at once and ran for the mill. For there below, gushing as it were from the bottom of the wall, was a little stream--a little fount equalling in bulk the tube-like shape formed by the swirling water he had noticed far above. The quantity was small, and quite a tiny stream ran down the valley, cutting itself a channelled course; but Will knew enough--knew the power of water, and what such a tiny stream could do. In short, in those brief moments he had grasped the fact that a dangerous flaw had been formed in the dam, which, if unchecked, might mean destruction to them all. "Father! Father!" cried Will, rushing into his father's bedroom. "I'm afraid it's worse, my boy," was the reply. "I'll lie still for a few hours and see if my headache passes off."