The centre of the pool was a black mirror that reflected an upside-down world. The water might have been knee-deep, or it might have been bottomless, there was no way of knowing, but William had the oddest feeling that if he fell into the water, he would find himself sinking down into that shadowy otherworld.

He did not like this place, not one little bit. It did not want him here, either. He was an intruder, an outsider. If he stayed much longer, he had the feeling he would be made to regret it.

With a huge effort, William threw the trap as hard as he could, out over the ice, towards the dark heart of the pool. There was a loud splash as it hit the water and sank beneath the surface.

He stepped back from the edge and watched the ripples die away. The water became still again. A movement of cold air touched his cheek and he turned quickly, grabbing a branch of the hazel tree to stop himself from falling backwards onto the icy margin of the pool. For a heart-stopping moment, he had the feeling that someone was standing close by. He could not see anything but he felt a presence so strongly, he could almost touch it.

"This will not be forgotten." The whispered words had no more substance than a breath of wind through branches.

William went hot and cold with terror. Forcing his shaking legs to move, he turned and ran.

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