Dickie was hopping excitedly on the edge.

"It's magic!" he shouted. "It's magic. It must be. It doesn't run away."

And he was right. The pool did not empty itself by another stream. The waterfall poured the water in, but it didn't run out. The pool was not very deep, but it was difficult to see the bottom for the rocks, and David supposed that the water escaped somewhere underground.

Richard started to clamber up the side by the waterfall. David called him back rather half-heartedly, and then Mary started after her twin. Although David felt somehow that this was a silly thing to do, he followed them because it would be exciting to see what was at the top. They pulled themselves up by holding on to heather roots, and half-way up David wished he had left the haversack behind. But he had to go on now, and when he was up it was worth it, for they were now in an even wilder and narrower gutter.

The stream was running fast through the heather, and behind them they could see the "rocky plateau", as Mary called it. This new valley was very tempting, but there was no path to follow - only the stream. It was here that David forgot Mrs. Ingles's advice to keep to the paths. Like the twins, he felt that this was real exploration at last, and they set out cheerfully enough into the unknown.

Macbeth found the going heavy. His legs were too short to allow him to see over the heather, and he soon exhausted himself with a series of kangaroo-like hops. Mary picked him up, but progress was difficult for them all. The heather dragged at their feet and scratched the twins' knees. David's haversack seemed to weigh a ton and Dickie's kettle clanked horribly as he struggled on.

The valley widened.

"Like a desert now," panted Mary.

"Where's the stream?" asked Dickie.

"Down to the right," said David. "We're going too high, and that's why it's so difficult. Follow me and we'll go lower down."

Suddenly the ground began to give under his feet. Each step forward squelched and he turned uphill again. Then the heather thinned and gave place to tufts of tussocky rushes and patches of bright green grass. When Dickie saw this open space he jumped onto it, then gave a shout of surprise.

When the other two turned he was floundering in black mud. Before they could help him a strange clear voice called out from somewhere above them, "Stand still! Don't hop about like that..."

They looked up in the direction of the voice and saw against the skyline a girl on a pony.

"Don't go too near him," she called again. "Tell him to stand still. I'm coming down."