“What on earth can it be?” gasped Whopper.  His face was deadly pale.

“Don’t ask me,” answered Snap.

“What’s up?” questioned Giant, who was a light sleeper, and the sound of his voice awoke the doctor’s son.  Soon he and the small youth were acquainted with what had occurred.

“Where did the voice go to?” asked Shep.

“It seemed to fade away in the air.”

“Why didn’t you take a shot at it?”

“How can you shoot something you don’t see?” demanded Snap, half indignantly.  “Just let me spot that ghost and I’ll show you what I’ll do!”

“Let us keep quiet,” suggested Whopper.  “Perhaps it will come back.”

All sat down around the fire, for further sleep was out of the question.  Thus an hour went by, but nothing came to disturb them.

“Looks as if the ghost business was finished for to-night,” remarked Shep, glancing around down the mountainside.  Then he leaped to his feet.  “Oh!”

“What did you see?” demanded the others, leaping up also.

“The ghost!”

“Where?”

“There—–­down among those tall trees.”

“I don’t see anything,” said Snap, after a careful look.

“It is gone now.  Oh, what a looking thing!” The doctor’s son was breathing heavily.

“Didn’t you imagine it?” asked Giant.

“No, I saw it as plain as day.”

“Yellow or white?”

“Yellow, and it had red horns, just as Ham Spink said.”

“Which way was it moving?”

“It seemed to be moving towards us, but it disappeared behind some rocks.”

After this the four boys were silent, straining their eyes and ears to see or hear the ghost.

“There it is!” fairly shouted Whopper, a minute later.

There was no need to utter the words, for the strange apparition was now in full view of all.  It resembled the body of a man, and glowed with a strange yellow light, while the horns of red waved menacingly toward them.

“Away! away! away!” came a deep voice.  “Go away from the mountain and the lake!” And then, raising a warning finger and pointing directly at the four young hunters, the ghostly, figure suddenly moved to one side and vanished!

CHAPTER XXX

THE SECRET OF THE MYSTERIOUS VOICE

“What do you think of that?”

Such was the question which several of the boys put to each other simultaneously.

“Why didn’t somebody shoot at the ghost?” asked Snap.

“Why didn’t you, Shep?” queried Giant.

“I—–­er—–­I forgot about it.”

“The ghost vanished too quickly,” said Snap.  “But keep on guard—–­it may come back.”

“If it does it will get something from me sure,” murmured the doctor’s son, and raised his shotgun.

“What do you think it was?” asked Whopper, after a painful pause of several minutes.