"I'm willing to stay," declared Hazel.

"Well, since I seem to be in the minority I'll have to give in," sighed Belle. "I'll stay if you all do, but I really think some one ought to be in this bungalow with us-one of the boys or--"

"I'll stay here," came from Jack, Walter, and Paul in a trio.

But when Mr. and Mrs. Floyd returned from town, and heard of the strange happenings, they offered to sleep in a small room opening off the living apartment.

The night, however, pa.s.sed without incident, though none of the girls slept well. Morning seemed to quiet the frayed nerves, and the happenings of the night before did not seem so mysterious in the glare of the golden sun.

The season for berries was at its height now, and as many varieties grew on the mountainside the young campers organized another expedition one day, about a week after the disturbance in which the light figured. Mrs.

Floyd promised to bake the pies if the boys and girls gathered the berries.

They planned for an all day stay, taking their lunch, and early in the afternoon all berry baskets were filled. Then, as there were some ominous-looking clouds in the west, they decided to start for the bungalows.

They were about half a mile from Camp Surprise, on a new short cut which Mr. Floyd had mentioned, when Cora, who was hurrying along in the lead, slipped on a slight declivity and, to save herself from falling, grasped a bush.

The bush, however, offered little hold, for it came away in her hand, and Cora slid on, until she brought up on a level place. She looked back, to join the others in the laugh at her slight mishap, when her eyes noted the place from which the bush had pulled away.

"Why look! Look here!" she called to the others. "Here's a regular cave!"

"A cave?" echoed Jack.

"Yes. There's a big hole which I'd never have seen only the bush became uprooted. Come here!"

"Come on!" cried Jack. "Let's see where this leads to. It may have something to do with the mystery."

"What mystery?" asked Bess.

"What mystery? The mystery of Camp Surprise! Maybe the boys hide in this cave. Come on!"

CHAPTER XXIII-THE TREMBLING NOISE

Jack, Walter, and Paul tore away more of the bushes screening the mouth of the natural cave. As they removed the leafy branches the black hole was seen to be of large size, fully high enough to permit even a tall man to enter without stooping, and wide enough to enable three to walk abreast.

"This is some cave!" exclaimed Jack. "I wonder Mr. Floyd never told us about it."

"Perhaps he didn't know," suggested Cora. "I wouldn't have seen it, and I was within a few feet of it, if I hadn't slipped and pulled away the bush."

"Well, we'll soon see if it amounts to anything," declared Paul, setting down the pail of berries he was carrying.

"Are you girls coming in with us?" asked Walter, looking at Cora and her chums who had not advanced.

"I don't know. Shall we?" asked Hazel, looking at her brother.

"I don't want to stay here," said Cora. "Besides, something might happen to the boys. But how are you going to explore the cave in the dark? And it is as dark as a bottle of ink in there. Have any of you your flashlights?"

"We can make a torch of wood," said Jack, when it developed that none of them had one of the pocket electric lights.

But just as Jack and the others were about to enter the cave the mutterings of thunder which had been increasing, culminated in such a clap that the girls, involuntarily placed their hands over their ears.

"Come on! Run for the bungalow!" cried Cora. "Else we'll be caught in a terrible storm! It's starting to rain now."

Some hot drops hissed down, the prelude to an almost tropical fury of the elements it seemed.

"We can go into the cave," suggested Paul.

"No!" cried his sister. "You shan't go in there with this storm coming up. The cave will keep. Come on, let's run!"

She darted off down the side of the mountain, the other girls following.

The boys hesitated a moment, and then, not wishing to desert the girls, even though the latter ran first, they followed.

"We can come back to the cave to-morrow," said Walter. "It won't run away. And to explore it well we ought to have the electric lights. Come on."

Paul and Jack followed him, and they all reached the girls' bungalow just as the deluge of rain came down.

For an hour or more the storm raged, blinding lightning and deafening thunder succeeding one another. But the bungalow was snug and safe, though once, when a tree was struck not far away, the girls screamed in terror.

That crash, however, seemed to be the culmination of the outburst, for from then on the rain began to slacken, and the thunder died away in muttered rumblings and the lightning became paler and paler until it was only a faint, shimmering light.

Then the dark sky cleared and the sun came out, shining through the storm-riven clouds and warming the ground and trees which were dripping from the vigorous bath.

"We got home just in time," commented Cora, as they looked out on the ceasing storm. "A little longer on the mountain and we would have been drenched."

"That cave was a find," commented Jack. "I want to see what's in it."

"Probably nothing more than a hole in the side of the mountain,"

commented Bess.

"I wouldn't be too sure of that," voiced Walter. "I wonder if Mr. Floyd knows anything about it?"

It developed that the caretaker did not, though he said there were several small mountain caves in that section, and this was probably one of them that he had not chanced upon.

"Do you think smugglers or pirates might have used it?" asked Hazel, with a smile.

"Hardly pirates," commented Jack. "Too far from the water. But smugglers might have done so. We're not so far from the Canadian line."

"All bosh!" declared Paul. "It's probably a garage dating from the stone age when the early inhabitants used the dinosaur as a jitney!"

They all laughed at his conceit and talked further of the cave and what they might find in it when they explored it the next day.

Whether it was the severe thunderstorm, or whether it was the culmination of the happenings of the past few weeks was not made clear, but it was certain that the girls, even Cora, were more nervous than they had been at any time yet.

"I-I wish we didn't have to stay here to-night," said Belle when supper was over, and they sat out on the porch, gazing into the fast-gathering darkness.

"Why?" asked Cora.