Coming through the darkness at a mad gallop was what seemed to be the gleaming skeleton of a horse. The ribs, the bones of the neck, legs and head, all showed plainly, glowing with a white light.

And on the back of the horse, which had sheered to the north and was passing the fire, sat what seemed to be the skeleton of a human being, the bones gleaming the same as those of the horse.

It was almost an astonishing and awe-inspiring spectacle, and it frightened the Indians greatly.

“Howugh—owugh—owugh!” wailed Black Feather, dismally.

Then the savages dropped on their faces, covering their eyes, so they could not see the skeleton horseman.

Almost at the same moment as the horseman was passing the spot the ghastly appearing thing seemed to give a sudden swing about and completely disappear.

“Poly hoker!” gasped Rattleton. “It’s gone!”

“That’s right!” palpitated Diamond—“vanished in a moment!”

“Oh, mah soul—mah soul!” wailed Toots. “Dat sholy am de ol’ debbil hisse’f, chilluns! When we see it next it’s gwan teh hab one ob us fo sho!”

“Hark!” commanded Browning.

The beat of the horse’s feet could be distinctly heard, but the creature had turned about and was going back toward the pass through the bluffs.

Chucker-chucker-chuck! chucker-chucker-chuck! chucker-chucker-chuck! came the ghostly sounds of the galloping horse.

“It’s turned about!” gasped Harry, in astonishment.

“It’s going!” fluttered Jack.

“And we’d better be going, too!” put in Browning.

Then with a familiar whirring sound something came flying toward them through the darkness, causing Toots to utter a wild shriek of terror.

Into the light of the camp-fire flashed a boy who was mounted on a bicycle, and they saw it was Frank Merriwell.

“Away!” he hissed, as he flew past them. “Make straight for the pass by which we entered this pocket. I will join you.”

Then he was gone.

Browning gave Toots a sharp shake, fiercely whispering:

“Mount your wheel and keep with us if you want to save your scalp! If you don’t you will be left behind.”

Then the boys leaped upon their bicycles and were away in a moment, before the prostrate Indians had recovered from the shock of terror given them by the appearance of the skeleton horse and rider.

For the time Bruce Browning took the lead, and the others followed him. Toots had heeded the big fellow’s warning words, and he was not left behind.

Barely had they passed beyond the range of the firelight and disappeared in the darkness when wild yells of anger came from behind them, and they knew the Indians had discovered they were gone.

“Bend low! bend low!” hissed Diamond. “They may take a fancy to shoot after us! Stoop, fellows!”

Stoop they did, bending low over the handlebars of their bicycles.

Bang! bang! bang!

The Indians fired several shots, and they heard some of the bullets whistle past, but they were not hit.

“Well, that’s what I call luck!” muttered the young Virginian.

“What do you call luck?” asked Rattleton.

“The appearance of that skeleton horse and rider in time to scare the Indians and give us a chance to get away.”

“Oh!” said Harry, sarcastically, “I didn’t know but it was Merry’s return. I told you he would not desert us.”

“I wonder how he happened to come back just then?”

“He came back because he was watching for an opportunity to help us, and he saw we had a splendid chance to get away while the redskins were scared by the appearance of the horse and rider. You ought to know him well enough to know he is not the fellow to desert his friends in a scrape like this.”

Diamond was silent.

“I wonder where Frank is?” said Browning. “He said he would join us, and he is——”

“Right here, old man,” said a cheerful voice, as a flying bicycle brought Merriwell out of the darkness to Browning’s side. “This way, fellows! We’ll hit the pass and get out of here as soon as we can.”

“Lawd bress yeh, Marser Frank!” cried Toots, joyfully. “I didn’t know’s I’d see yeh no mo’, boy!”

“I hope you didn’t think I had left you for good?”

“No, sar!” declared the colored boy. “I done knows yeh better dan dat, sar! I knowed yeh’d come back, but I was afeared yeh’d come back too late, sar. Dem Injunses was gittin’ po’erful anxious fo’ dis yar wool ob mine—yes, sar!”

“Well, I am glad to know you thought I would not desert you. I don’t want any of my friends to think I would go back on them in the hour of need.”

Diamond was silent.

The pass was found without difficulty, and they went speeding through it.

“How did you happen to turn up just then, Frank?” asked Harry.

“I was waiting for a chance to come to you, and I saw the chance when that horse and rider frightened the Indians.”

“The horse and rider—where are they?” asked Browning.

“Gone through the pass ahead of us.”

“Mah gracious!” exclaimed the colored boy. “What if dat ol’ debbil teks a noshun teh wait fu’ us?”

“What sort of ghost business was it, anyway?” questioned Rattleton. “It seemed to be a skeleton horse and a skeleton rider, and it disappeared in a twinkling. I will admit this skeleton business is beginning to work on my nerves.”

“It is rather creepish,” laughed Frank; “but I do not think it is very dangerous.”

“All the same, you do not attempt to explain the mystery.”

“Not now.”

“Not now? Can you later?”

“Perhaps so.”

“It is plain he knows no more about it than the rest of us,” said Diamond. “As for me, I am getting sick of seeking vanishing lakes and vanishing skeletons. If I get out of this part of the country alive, you’ll never catch me here again.”

“Meh, too!” exclaimed Toots.

“Well, I don’t know as any of us will care to revisit it,” laughed Frank. “Anyway, we have been very lucky in escaping from those Indians. That you can’t deny.”

“You fooled them easily,” said Rattleton.

“Yes, and they did not even take a shot at me, which was a surprise. I expected they would pop away a few times.”

“What are we going to do after we get out on the open desert again?” asked Jack. “It seems to me we’ll be as bad off as ever.”

“We’ll have to go around the range to the south, or wait for the Indians to get away from that water-hole, so we can go through the mountains as we originally intended.”

“The Indians may not go away.”

“I rather think they have been scared so they’ll not hang around there long. I don’t fancy they’ll be anywhere in the vicinity by morning.”

“If they are gone——”

“We’ll be all right, providing we can make our hard bread and dried beef hold out till we can reach one of the small railroad towns.”

“How far away is the railroad?”

“Not much over fifty miles.”

“That is easy!” declared Rattleton. “We can make it on a spurt!”

As they reached the eastern opening of the pass their attention was attracted by a bright light that seemed to shine out from the very niche where they had found the jewel-decorated skeleton.

“What does that mean?” exclaimed Jack, in astonishment.

“Land ob wartermillions!” gasped Toots. “It am de debbil’s light fo’ suah, chilluns! Don’ yeh go near it!”

“By Jove!” cried Frank. “That is worth investigating! Come on, fellows!”

He headed straight toward the light, and as they came near the niche they saw the bejeweled skeleton was again seated as they had seen it in the first place, and a bright flood of light was shining upon it from some mysterious place.

“It’s back!” exclaimed Harry, in astonishment.

“Sure enough!” said Frank. “It is on deck again.”

“I tells yeh to keep away from dat skillerton!” shouted Toots. “Hit am gwan teh grab yo’ this time if yo’ gits near hit!”

“We’ll take chances on that,” declared Frank. “This time we won’t give it time to get away, but we’ll go right up and examine it.”

“That’s what we will!” agreed Harry.

But even as he spoke, the light disappeared, and this made it impossible for them to see anything up there in that dark nook.

“Ha! ha! ha!”

Again they heard the mocking laughter, smothered, hollow and ghostly in sound.

“Somebody is having lots of fun with us,” said Frank, as he leaped from his wheel. “It may be a good joke, but I fail to see where the ‘ha, ha,’ comes in.”

“Is the skeleton gone?”

“I don’t know, but I’ll mighty soon find out.”

Without hesitation he swung himself up to the niche in the rocks, and Rattleton followed, determined that Frank should not go alone into danger.

Harry afterward confessed that he was shivering all over when he climbed up there in the darkness, but his fear did not keep him from sticking to Merry.

A cry broke from Frank’s lips.

“What is it?” called Browning, from below.

“By the eternal skies, it’s gone again!”

“Didn’t I tole yeh!” cried Toots, from a distance. “Come erway from dar, Marser Frank! If yo’ don’, yo’s gwan teh be grabbed!”

“It is gone!” agreed Rattleton. “This beats the Old Nick!”

Again they heard that mocking laugh, which seemed to come down from some point above their heads.

“Wooh!” shivered Harry. “That sounds pleasant!”

“Hang it all!” exclaimed Frank, in a voice that indicated chagrin. “I don’t like to be made fun of this way! If we don’t solve this mystery before we go away I shall always regret it.”

“Beware!”

It was the same voice that had uttered the warning when they were riding into the pass, and now, in the darkness of night, it sounded even more dismal and uncanny than before.

“Come out and show yourself,” called Frank.

For some time the boys remained there, but they were forced to abandon the task of solving the mystery that night. Frank descended to the ground with no small reluctance, and Harry kept close to him. They mounted their wheels and rode away once more, fully expecting to hear the mocking laughter, or the ghostly voice calling after them. In this, however, they were disappointed, as nothing of the kind happened.

After they had ridden some distance, Frank proposed that they halt for the night.

“We are in for an open-air camp to-night,” he said. “It is something we did not expect, but it can’t be helped, and as the night is not cold I think we can get along all right. We need rest, too.”

“That’s right,” agreed Bruce. “I feel as if I need about a week of steady resting, but I don’t care to take it here.”

“How about the Indians?” asked Jack. “We are not very far from them, and they might find us.”

“I scarcely think there is any danger of that.”

“Why not?”

“Those redskins were so badly frightened that they’ll not go hunting after white boys to-night. It is more likely they will skin out and make for the Shoshone Reservation, on which they must belong.”

“But what if they should happen to follow us?” Jack persisted.

“We must take turns at standing guard to-night, and the guard should be able to give us warning of danger in time for us to mount our wheels and get away.”

It was plain that Diamond was not in favor of stopping there, but he said no more.

Fortunately the night was warm, so they suffered no discomfort by sleeping thus. No dew fell out there on the desert.

It was arranged that Diamond should stand guard first, while Frank came second, with Toots for the last guard toward morning.

They ate some of the hard bread and jerked beef and then threw themselves down, with their bicycles near at hand, so they could spring up and mount in a hurry if necessary.

Browning was the first to stretch himself on the ground, and he was snoring almost immediately. The others soon fell asleep.

The rim of a round, red moon was showing away to the eastward when Jack awoke Frank.

“How is it?” Merriwell asked. “Have you heard or seen anything suspicious?”

“Not a thing,” was the reply. “All is still as death out here—far too still. I don’t like it.”

“Well, it is not real jolly,” confessed Frank, with a light laugh; “but I don’t think we need to be worried about visitors; and that is one good thing.”

Jack was fast asleep in a short time.

Morning came, and Toots was the first to awaken. Dawn was breaking in the east as he sat up, rubbing his eyes and muttering:

“Good land! dat am de hardes’ spring mattrus dis coon ebber snoozed on—yes, sar! Nebber struck nuffin’ lek dat befo’.”

Then he looked around in some surprise.

“Gracious sakes!” he continued. “Whar am de hotel? It done moved away in de night an’ lef’ us.”

It was some time before he realized that they had not put up at a hotel the night before.

“Reckum dis is whar we stopped las’ night,” he finally said. “I ’membah ’bout dat now. We was ter tek turns watchin’. I ain’t took no turn at all, an’ it’s wamnin’. He! he! he! Guess de chap dat was ter wake me fell asleep hisself an’ clean fergot it. Dat meks meh ’bout so much sleep ahaid ob de game.”

He was feeling good over this when he noticed that three forms were stretched on the ground near at hand, instead of four.

“Whar am de odder one?” he muttered. “One ob dem boys am gone fo’ suah. Land ob wartermillions! What do hit mean? Dar am Dimun, an’ dar am Rattletum, an’ dar am Brownin’, but whar—whar am Marser Frank?”

In a moment he was filled with alarm, and he lost no time in grasping Harry’s shoulder and giving it a shake, while he cried:

“Wek up heah, yo’ sleepy haid—wek up, I tells yeh! Dar’s suffin’ wrong heah, ur I’s a fool nigger!”

“Muts the whatter?” mumbled Rattleton, sleepily. “Can’t you let a fellow sleep a minute? It isn’t my turn yet.”

“Yoah turn!” shouted Toots. “Wek up, yo’ fool! It’s done come mawnin’, an’ dar’s suffin’ happened.”

“Eh?” grunted Harry, starting up and rubbing his eyes. “Why the moon is just rising.”

“Moon!” snorted the colored boy. “Dat’s de sun comin’ up! An’ I don’t beliebe yo’ took yoah turn keepin’ watch.”

Browning grunted and rolled over, flinging out one arm and giving Toots a crack on the neck that keeled him over on the ground.

“Landy goodness!” squealed the darky, grasping his neck with both hands. “What yo’ tryin’ ter do, boy? Want ter coon? Nebber seen such car’less pusson, sar!”

“Oh, shut up your racket!” growled the big college lad. “I’m not half rested yet. Call me when breakfast is ready.”

“Yo’ll done git yeh own breakfas’ dis mawnin’, sar; but befo’ dar’s any breakfas’ we’s gwan ter know what has become of Marser Frank. He’s gone.”

“Gone?” replied Bruce, sitting up with remarkable quickness.

“Gone?” ejaculated Harry, popping up as if he were worked by springs.

“Gone where?” asked Diamond, also sitting up and staring around.

“Dat’s jes’ what I wants ter know, chilluns,” declared Toots. “Dat boy ain’t heah, an’ I’s po’erful feared de old skillerton debbil has cotched him.”

“Why—why,” said Jack, “I woke him and he took my place.”

“But nobody roused me,” declared Rattleton.

“Nor me,” asserted Browning.

“Git up, chilluns—git up!” squealed Toots, excitedly. “We’s gotter find dat boy in a hurry! ’Spect he’s in a berry bad scrape!”