The sound came once more through the darkness to the little Bobbsey twins, and as they listened to it Flossie and Freddie looked at one another in surprise. They could just dimly make out the faces of each other in the dimness.

"Mamma! Mamma!" cried a voice, for it was a voice that had caused the queer sound; yet it did not sound like the voice of man, woman or child. "Mamma! Mamma!" it cried.

"Hear it?" asked Flossie again.

"Yep," answered Freddie. "It's a little boy or girl—like us—an' it's in this cave. I guess lots of childrens get lost here like us. Now I'm not afraid."

"Mamma! Papa! Mamma!" came the voice again.

"It—it's kind of funny," whispered Flossie to Freddie. "Don't you think it's kind of funny, Freddie?"

"Yes, but I know what makes it."

"What?"

"It's being in this cave. You know how we used to holler at the hill, when we went to the country—'member that?"

"Yep," answered Flossie.

"An' how our voices used to come back an' sort of hit us in the face?" went on her brother.

"Yep."

"Well, that was an echo," said Freddie, "an' that's what makes it sound so queer here. It's an echo."

"Oh," said Flossie. She had not thought of that.

Once more the voice sounded out of the darkness.

"Mamma! Papa! Mamma!"

"There! Hear it? It's an echo!" cried Freddie.

Flossie listened a moment. Then she said:

"If it was an echo, Freddie, why didn't your voice echo too?"

"Oh,—er—well—'cause I didn't want it to," Freddie made answer. "I can do it now. Hello! Hello! Hello!" he called as loudly as he could.

And then, to the surprise of the children, back came a voice in answer, and in more than an answer, for it asked a question. No longer did the voice call: "Mamma! Papa!"

Instead it cried:

"Hello, there! What's the matter? Who are you and what do you want? Where are you?"

Flossie and Freddie were so startled that, for a moment, they could only hold on to each other in the darkness.

Then Freddie found his voice enough to speak. He said:

"Did you hear that echo, Flossie?"

"That wasn't an echo," declared his little sister quickly. "Echoes only say the same things you say and this—this was different."

"Yes, it was," Freddie agreed. "But maybe it's a different kind of echo."

"Try it again," suggested Flossie, when they had remained quietly in the darkness for a time. And during that time they had not heard the strange voice calling. It seemed to have been hushed after the "echo," if that is what it was, made answer. "Call again," Flossie begged her brother. Once more he called:

"Hello! Hello! Hello!"

"Well, what do you want?" back came a voice in question. This time there was no doubt about its not being an echo. It had not repeated a single word that Freddie had cried.

"Oh, how funny!" cried Flossie. "What makes it do that?"

Before Freddie could answer, even if he had known what to say, the two children saw a light coming toward them. It was the light of a lantern, bobbing about in the darkness, and because it was a light, which chased away some of the gloom, they were glad, even though they had been a bit frightened by the queer voice and the echo which did not repeat words as the other echo had done.

"Oh, maybe it's daddy and Bert come to look for us!" cried Flossie eagerly.

Freddie thought the same thing, for he called out:

"Here we are, Daddy!"

But, to the surprise and disappointment of the children, a surly voice answered them:

"I'm not your father! Who are you, anyhow, and what are you doing in this cave?"

Flossie and Freddie, clinging to each other, shrank back in fear. Then, as the light came nearer, they saw that the lantern was carried by a tall man—a man with a very dark face. He had gold rings in his ears, on his feet were big boots, and around his neck was a bright yellow handkerchief.

"Oh!" gasped Flossie. "Oh, he—he's a gypsy!"

Freddie saw it, too. The man seemed surprised to see the children. He gave a sort of grunt, held the lantern up to their faces, and exclaimed:

"Why, there's two of 'em!"

"Yes, we—we're twins!" stammered Flossie.

"Twins are always two," Freddie added, thinking, perhaps, that the gypsy man did not know that.

"Twins, eh?" remarked the man in a questioning voice.

"The Bobbsey Twins," said Freddie. "We came from our camp, and we——"

"How'd you get in this cave? That's what I want to know!" cried the man, and he spoke harshly. "Tell me, how did you get here?" he asked, and he held the lantern in front of the faces of the two little children.

"We—we fell in here!" said Freddie, pushing Flossie behind him. He felt that he must look after his little sister and protect her.

"Fell in?" cried the man.

"Yes, through a hole. We slid down a sandy hill, and we couldn't climb back again. We saw a little light over this way and we walked to it and then we heard some one cry: 'Mamma!' Are there any more little children here?" Freddie asked.

"Hum! Yes, some," half-grunted the gypsy. "But not your kind. I don't see how you came here," he went on, speaking to himself, it seemed, for he did not glance at Flossie or Freddie and there was no one else near by. The man looked all about the cave.

"Which way did you come?" he asked.

"Back there," and Freddie, who was doing most of the talking, pointed toward the place where he and Flossie had tried so hard to climb up.

"Come and show me," the man ordered them, and when they walked back with him, the lantern making queer shadows on the side walls of the cave, Flossie and Freddie pointed to the place down which they had slid.

"Hum!" murmured the gypsy. "I never knew there was a way into the cave from there. I must see about that. It wasn't open before. Well, now you're here I've got to make up my mind what I'll do with you," he went on, as he motioned for Flossie and her brother to walk back in front of him. He held the lantern so they could see where to step, but the earthen floor of the cave was smooth, and the children did not stumble.

"Will you take us back to Twin Camp, where we live?" asked Freddie. "We're the Bobbseys you know, and we didn't mean to run away again, though I guess we're lost. My mamma and my papa will be looking for us, and if you'll take us to the camp——"

"Well, maybe I will after a bit, but not now," said the gypsy, shaking his head so that his earrings jiggled. "You'll have to stay here with us awhile. If you went out now, and told your folks you had found us here we'd all be sent to jail, most likely. I'll see what the others say."

Flossie and Freddie wondered what others he meant, but he did not tell them. He kept walking close behind them, and there was nothing for them to do but to keep on.

Suddenly they turned a sort of corner of the cave, and then the children saw something that surprised them. Seated around a table, on which some candles, stuck in bottles, were burning, were a number of men. They were all gypsies, like the man who had met the children farther back in the cave, and as he walked forward, behind Flossie and Freddie, the other gypsies looked up.

"Who was calling?" asked one of the dark men at the table.

"These two," said the first man, pointing to the little Bobbsey twins. "They answered my call and I found them. They fell down a hole at the far end of the cave, near the sand. I never knew it was there."

"It is an old entrance," put in a gypsy who was eating some bread and tomato, cutting first a slice of one and then of the other with a big knife. "That entrance was overgrown with grass long ago," he added.

"Well, these two stumbled on it," grumbled the man who had found Flossie and Freddie. "We'd better stop it up. And now what's to be done with 'em?"

"We'll have to keep 'em here for a while," said two or three at once, and hearing this the hearts of Flossie and Freddie were sad.

"Yes," went on the first gypsy, "we'll have to keep 'em here until we're ready to go, and that won't be for two or three days yet. The only trouble is that some of their folks may find where we have hidden 'em and——"

"Hi!" suddenly cried an old gypsy, and then he said something very quickly, but in words the children could not understand. It was gypsy talk. After that all the men spoke in this queer way, but Flossie and Freddie felt sure they were being talked about, for the men looked at them many times in the light of the lantern and candles.

Suddenly, when there came a lull in the talk, and the twins were wondering what was coming next, they heard a dog barking. Now, ordinarily, this would not have surprised them, for they knew the gypsies kept many dogs, and some might be in the cave. But there was something different about this bark.

In wonder Flossie and Freddie looked at each other. Then Freddie cried out:

"That sounds like Snap!"

All at once there came a regular chorus of barks, and with them a man's voice could be heard shouting. Then came a dog's growl and yells from a man's voice, then more barks.

"Look out!" shouted some one in the cave. "The dog's loose!"

Flossie and Freddie saw a big dog spring into view from somewhere out of the darkness of the cave, and as the eyes of the twins lighted on him, Freddie cried:

"Here comes Snap! Here comes Snap! Oh, Flossie! our dog that was lost is found! Here's Snap!"