"Am I seeing things? Look! Over there on that hill!"

Following her gaze, the girls were astonished to see shadowy white figures flitting about in the moonlight.

"Ghosts!" Bess exclaimed.

"Ghosts nothing," George retorted. "There's no such animal!"

Don't be alarmed," Joanne said with a smile. "I imagine the members of the nature cult are having one of their festive airings by the light of the moon!"

The girls watched the cult members go through their mystic rites.

"They're not doing much of anything," Nancy observed, "except napping around."

Within ten minutes the ceremony apparently was concluded. The white figures clustered together for a moment, then moved off across the hillside.

"I wonder where they're heading," Nancy mused. "Back to their tents?"

Joanne had been watching intently. Now she shook her head. "I don't think so. I forgot to tell you-the cave has another opening on the slope of the hill, near the river. The colony members are going in that direction."

Immediately Nancy's curiosity was aroused. Did this mean the white-robed group intended to go into the cave itself? If so, why? To continue the ceremony?

"It certainly was a short performance," Bess remarked as the mysterious "dancers" vanished from sight. "I wonder if the ritual has any significance."

"That's what I'd like to know," Nancy said quietly. "And that's what we must find out!"

"Not tonight!" Joanne said firmly. "Grandmother will be very upset if we don't come right back."

Reluctantly Nancy gave up the idea. The girls started for the farmhouse, but Nancy kept looking back over her shoulder, determined not to miss anything. However, the hillside remained uninhabited and still.

As the girls drew near the road, the motor of a car broke the silence and headlights appeared. The automobile slowed down in front of the farmhouse as if about to stop. Then suddenly the car went on. Why? Nancy wondered. Had the driver seen the girls and changed his mind?