"Yes, I heard it. I wonder----"

"Hark!" whispered Flossie. "There it goes again!"

CHAPTER XXI

"HERE COMES SNAP!"

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. h.e.l.lo! h.e.l.lo! h.e.l.lo!" 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:

"h.e.l.lo, 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:

"h.e.l.lo! h.e.l.lo! h.e.l.lo!"

"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!"