They were now on a wide plateau and their track joined another bridle path running north and south along the top of the mountain.

"That pile of stones marks the top of the Mynd," said Peter pointing ahead. "Quite near there is the most secret of all my hidden dells. You'll be the first ever to see it and hide in it. Let's go there now."

Dickie was still protesting that he wanted to climb the cairn and see the Devil's Chair before he did anything else when Peter disappeared. One second she was there - and the next she wasn't! While they were staring at each other in bewilderment there was a snuffling noise and Macbeth vanished too. Then Peter's laugh came almost from their feet, and they realized that her dell was so well hidden by the overhanging heather that they were within a few feet of it without knowing. They jumped in and the heather closed over their heads. Macbeth suddenly cocked his head and growled.

David put his hand on his collar, and the others stopped talking.

"Quiet," whispered Peter. "Someone's coming."

"The enemy approaches stealthily," said Dickie,,

"Right into the ambush," added Mary.

Peter put a finger to her lips and knelt upright so that she could peep through the heather. Then she turned and beckoned David up beside her while the twins patted Macbeth so that he would not bark.

About fifty yards away a man was standing in the track. He was wearing a fawn raincoat, and had a knapsack on his back. He looked hot and tired and rather cross, and while they watched him he pushed his soft felt hat to the back of his head and began to search through his pockets. David saw him glance at the cairn of stones which marked the summit, then he pulled out a piece of paper, unfolded it and studied it intently.

"He's lost," whispered David. "Shall we go and help him?"

"No," said Peter doubtfully. "Let's not. I've got an idea. Let's trail him and see where he's going... I wonder what he's doing up here at this time by himself?... On a walking tour I s'pose... Shall we, David? Shall we follow him just for fun? It'll be good practice."

Suddenly they could hear the stranger's steps coming nearer. He was whistling quietly as he passed just above their heads. They lay quiet for a little and then Peter said, "Are you all game for a real adventure? Are you ready to track him to his hiding place------"

"Lair," interrupted Dickie.

"Course we are," said Mary. "Think we can't trail? Course we can. Just like Indians."

"Glad I left that old kettle behind," said Dickie, solemnly. "Red Wolf no track paleface with kettle."

"Tiger Lily put on moccasins," added Mary inconsequently.

"You know where we are, Peter," said David, "so you'd better be leader. I'll come next. Then Dickie and Mary and Macbeth."