"Because I-I'm afraid. Come now, aren't you?" she challenged.

"Well, I can't say I like all the mysterious happenings," Cora admitted.

"And now that we know there is a cave near us-more than one perhaps-and that we don't know who-or what-may be in them, why, I can't say it is the most pleasant vacation we have experienced."

"This bungalow gives me the creeps!" complained Hazel.

"Why not take ours?" suggested Walter. "It's large enough for you to sleep in, and we'll take this one. Come on, what do you say?"

"No, not to-night anyhow," decided Cora. "We'll keep to our agreement and stay here. Mrs. Floyd will be here with us."

"And not Mr. Floyd?" asked Belle.

"No, not until later. He has to go to some town meeting I believe, and will come in around midnight. But nothing has happened in the last few days-not even a noise."

"I've heard noises," confessed Belle.

"What sort?" Jack inquired.

"Oh, sort of rumbling, trembling noises, and they seemed to be away down under the ground. I heard one yesterday, when I came back to get my veil after the others had gone out. It scared me," Belle added.

"I think the waterfall causes those rumbling noises," said Walter.

"We'll have to investigate that to-morrow."

The boys went to their own bungalow, and Mrs. Floyd came in to occupy the small temporary bedroom. Her husband would be in later, she explained, confirming Cora's information in that respect. The thunderstorm had cooled the rather oppressive air and there was a refreshing breeze blowing as the girls went up to their bedrooms.

Just who awakened first, it would be hard to say. Probably it was Belle, as she was the lightest sleeper. Cora heard her calling, and at the same time she was aware of another disturbance.

"Do you hear it?" asked Belle from her room.

"Yes," Cora answered. At the same time she could hear Bess and Hazel getting up.

The whole bungalow seemed filled with a roaring, trembling noise, and there was a slight vibration of the building.

"What is it? Oh, what is it?" cried Belle, in hysterical tones.

"I don't know," answered Cora. "But I'm going to find out."

"How?"

"By calling the boys. Mrs. Floyd, are you awake?" Cora demanded, going to the head of the stairs.

"Yes. That noise awoke me."

"Is Mr. Floyd home?"

"Not yet."

"Then I'm going to telephone for the boys!"

CHAPTER XXIV-THE SECRET Pa.s.sAGE

Hastily donning robes and slippers, the girls gathered about Cora as she rang the electric bell which had been arranged to summon the boys in the other bungalow to the toy telephone. Meanwhile, Mrs. Floyd had arisen and dressed to let in the boys. The rumbling, trembling noise had stopped.

"Oh, why don't they answer?" cried Cora, impatiently pushing the electric bell b.u.t.ton again and again.

Then, through the toy receiver came a faint voice.

"h.e.l.lo! h.e.l.lo, there! Is that you, girls? What is the matter?"

"This you, Jack?" Cora asked.

"Yes."

"Come over as fast as you can! Hurry!"

"What's the matter?" he asked.

"Don't stop to question! Hurry over!" Cora begged. "It's that terrible noise again. Can't you hear it?"

"No," answered Jack. "But we'll be right over. Come on, fellows!" Cora heard him call to Walter and Paul, as he left the telephone. "The girls are scared."

"I guess he'd be too, if he heard that noise," Cora said. "Did you all hear it?" and she appealed to her chums.

"I did," affirmed Hazel. "It sounded like distant thunder."

"Could it have been?" asked Mrs. Floyd, who had joined the girls.

"The stars are shining," reported Belle, looking from a window, shading her eyes with her hands from the light in the room. They had partly dressed and gone down to the living room. There they listened and waited both for a recurrence of the noise and for the approach of the boys.

The latter made their presence known first, fairly running along the graveled way that led from their bungalow, over the rustic bridge, to the girls' abiding place.

"What's all the racket about?" demanded Jack, as he and his two chums entered, rather breathless from their run and their hurry in dressing, the hurry showing itself in the absence of collars and ties.

"It's that noise," said Cora, her voice trembling slightly. "We heard it again, Jack."

"Was it so scary?" demanded Paul, looking at his sister.

"It certainly was-too scary for words!" answered Belle. "I'm not going to pa.s.s another night in Camp Surprise!"

"It _has_ been a surprise with a vengeance," declared Bess. "Boys, can't you do something?" she appealed.

"What's to be done?" asked Jack. "We'll have to wait until we hear the noise again, and then we can tell from which direction it comes.

Suppose, while we're waiting, you girls just tell us what you heard."