CHAPTER VIII.

  THE MYSTERY EXPLAINED.

  By this time the boys were fully aroused. An investigation showed thatMerriwell's wheel was gone.

  "Didn't I tole yeh old debbil skillerton would done cotch some ob us!"cried Toots, in great distress.

  "I hardly understand what the skeleton could have wanted with Merry'swheel," observed Browning.

  "G'way dar, boy! Didn' de skillerton ride a hawse!"

  "And you think it is an up-to-date skeleton that has decided to ride abicycle hereafter. In that case, I congratulate Mr. Skeleton on hisgood sense."

  "It must be that Frank has gone on a ride without saying anything tous," said Jack. "I do not see any other way of explaining it."

  "But why should he do such a thing?" asked Rattleton.

  "That is where you stick me."

  Browning slowly shook his head.

  "It is remarkable that he should do such a thing without sayinganything to us," declared the big fellow.

  "And he must have taken that ride in the night," said Jack.

  "While he should have been on guard," added Harry.

  The boys stood looking at each other in sober dismay.

  "It isn't possible that Merry could have gone daffy," mutteredRattleton. "He is too well balanced for that."

  "I don't know," came gloomily from Diamond. "This dismal, burningdesert is enough to turn the brain of any fellow."

  "Yah!" cried Toots. "Don' yeh git no noshun dat boy ebber had hisbrain turned! It am de weak brains dat git turned dat way. His brainwas all right, but I jes' know fo' suah dat he hab been cotched."

  "And I suppose you want to run away as soon as possible before you are'cotched?'"

  Then the colored boy surprised them all by saying:

  "No, sar, I don' want teh go 'way till we knows what hab become obMarser Frank. Dat boy alwus stick by his frien's, an' dis coon amreddy teh stick by him, even if he do git cotched."

  "Good stuff, Toots!" cried Rattleton, approvingly. "You are all right!If anything has happened to Frank we'll know what it is or leave ourbones here."

  The boys were worried. They hurriedly talked over the remarkabledisappearance, trying to arrive at an understanding of its meaning.

  At length it was agreed that Frank might have gone back to try tosolve the mystery of the skeleton, and then they decided that two ofthe party should remain where they had made their night bivouac, whilethe other two proceeded to search for Merriwell.

  Diamond insisted on being one of the searchers, and Rattleton wasdetermined to be the other, so Browning and Toots were left behind.

  The boys mounted their wheels and rode back toward the pass throughthe bluffs.

  Diamond was downcast again.

  "Everything is going against us," he declared. "There is fate in it. Iam afraid we'll not get out of this wretched desert."

  "Oh, you're unwell, that's what's the matter with you!" declaredHarry, scornfully. "I'll be glad when you are yourself again."

  "That's all right," muttered Diamond. "You are too thoughtless, that'swhat's the matter with you."

  They approached the spot where the mysterious skeleton had been seen,and both were watching for the niche in the rocks.

  Suddenly they were startled by hearing a wild cry from far above theirheads, and looking upward they saw Frank Merriwell running along thevery brink of the cliff, but limping badly, as if he were lame.

  But what astonished and startled them the most was to see astrange-looking, bare-headed man, who was in close pursuit of Frank.Above his head the man wildly flourished a gleaming, long-bladedknife, while he uttered loud cries of rage.

  "Smoly hoke!" cried Harry. "Will you look at that!"

  Diamond suddenly grew intensely excited.

  "What can we do?--what can we do?" he exclaimed. "Frank is hurt! Thatcreature is running him down! He will murder him!"

  "If Merry had a pistol he would be all right."

  "But he hasn't! We must do something, Harry--we must!"

  "Neither of us has a gun."

  "No, but----"

  "We can't get up there."

  "But we must do something!"

  "We can't!"

  Jack grew more and more frantic. He leaped from his wheel and seemedto be looking for some place to try to scale the face of the bluff.

  "Oh, if I could get up there!" he groaned. "I'd show Frank that I wasready to stand by him! I'd fight that man barehanded!"

  And Rattleton did not doubt it, for he well knew how hot-bloodedDiamond was, and the young Virginian had never failed to fight whenthe occasion arose. He would not shirk any kind of an encounter.

  Merriwell saw them and shouted something to them, but they could notunderstand what he said.

  "Turn! turn!" screamed Jack. "You must fight that man, or he will stabyou in the back! He is going to strike you!"

  Frank seemed to hear and comprehend, for he suddenly wheeled about andmade a stand. In a moment the man with the knife had rushed upon himand struck with that gleaming blade.

  A groan escaped Jack's lips as he saw that blow, but it turned to agasp of relief when Frank stopped it by catching the man's wrist.

  "Give it to him! Give it to him!" shrieked Diamond, dancing around ina wild frenzy of anxiety and fear.

  Then the boys below witnessed a terrific struggle on the heights abovethem.

  The man seemed mad with a desire to plunge the knife into Frank, andit was plain that Merriwell did not wish to harm the unknown, but wastrying to disarm him.

  "What folly! what folly!" panted Diamond. "He'll get his hand free andstab Merry sure! Beat him down, Frank--beat him down!"

  Once Frank slipped and fell to his knees. A fierce yell of triumphbroke from the man, and it seemed that he would succeed in using theknife at last.

  With a groan of anguish Diamond covered his eyes that he might notwitness the death of the friend he loved. For Jack Diamond did loveFrank Merriwell, for all that he had complained against him of late.

  A cry of relief from Rattleton caused Jack to look up again, and hesaw Frank had regained his feet and was continuing the battle.

  And now the man fought with a fury that was nerve thrilling towitness. His movements were swift and savage, and he tried again andagain to draw the knife across Frank's throat.

  Jack and Harry scarcely breathed until, with a display of strength andskill, Frank disarmed his assailant by giving his arm a wrench,causing the knife to fly through the air and fall over the edge of thecliff.

  Down to the ground below rattled the knife, and then Diamond said:

  "Now Frank will be able to handle the fellow!"

  But, flinging his arms about the boy, the man made a mad effort tospring over the brink. For some seconds, locked thus in each other'sarms, man and boy tottered on the very verge, and then they swayedback.

  Frank broke the hold of the man, striking him a heavy blow a secondlater. The man reeled and dropped on the edge of the precipice. Hescrambled up hastily, but a great slice of rock cleaved off beneathhis feet and went plunging downward.

  Then the watching boys saw the unknown tottering on the brink, wildlywaving his arms in an endeavor to regain his balance. Frank sprangforward to aid him.

  Too late!

  With a wild scream of despair, the strange man toppled over andwhirled downward to his death.

  Frank climbed down.

  "It's all up with him, poor fellow," said he, as he stood near thebody of the unknown man, looking down at the face that was white andcalm and peaceful in death.

  "Who is he?" asked Harry.

  "What is he?" asked Jack.

  "I am afraid those questions cannot be answered," confessed Frank."That he was a raving maniac I am sure, and he lived in a remarkablecave close at hand; but who he is or how he came to be there in thatcave I do not know."

  "Well, how you came to be up there with him running you down to sticka knife in you is what I want to know," said Harry.

  "That's right," Jac
k nodded. "Explain it, old man."

  Then Frank told them how, after the moon rose the night before, he hadtaken his wheel with the intention of riding around the camp, feelinghe could keep watch as well that way as any. After the moon was wellup, he saw there was no one anywhere about, and a desire to revisitthe spot where they had seen the skeleton seized upon him. He rode tothe spot, but there was no skeleton in the niche among the rocks.Leaving his bicycle, he climbed up there to examine once more, and tohis astonishment, found that what seemed to be a solid, immovablestone had turned in some manner, disclosing an opening.

  Then, with reckless curiosity, Frank resolved to investigate further,and he descended into the opening, found some stone steps, and wassoon in a cavern. The first thing he discovered was the skeleton,still decorated as the boys had seen it in the first place, and heremained there till he found how it could be placed in view on theblock of stone and then removed in a twinkling. He also found a lampwith a strong reflector, which had thrown its light on the skeletonfrom a hole in the rocks. There was another opening near that, where aperson in the cave could look out on the desert, and Frank knew theghostly voice they had heard must have come from that place.

  Merriwell continued his investigations, having lighted the lamp, bythe light of which he wandered through the cave. Suddenly he came faceto face with an old man, who seemed surprised, but spoke quietly tohim.

  The old man declared he was "Prof. Morris Fillmore," but did not saywhat he was professor of, and he volunteered to explain everything tothe boy.

  This he did, telling how he worked the skeleton to frighten away thosewho might molest him in his solitude, as he wished to be alone. Therewas another entrance to the cave, and, in a large, airy chamber ahorse was kept. The horse was coal black, but on one side of him wasdrawn the outlines of the skeleton frame of a horse, and the strangeold man explained that he had a suit of clothes on one side of whichhe had traced the skeleton of a human being. This had been done withphosphorus, and it glowed with a white light in the darkness.

  The old hermit had entered the pocket and ridden near the camp of theIndians. When he turned about the skeleton tracings in phosphoruscould not be seen, and so the ghostly horse and rider seemed todisappear in a most marvelous manner.

  Frank questioned him concerning the treasure, and the old man seemedto grow excited and suspicious. He said something about the treasurebeing the property of some one who had fled from the destroying angelsof the Mormons in the old days, but had perished in the desert. Frankwas led to believe that the skeleton was that of the original owner ofthe treasure.

  But when the boy would have left the cave the stranger told him hecould not do so. He informed Frank that he could never go out again,and then it was that the boy became sure Fillmore was crazy.

  As the man was armed, Frank decided to use strategy. First he soughtto lull the man's suspicions, and after being watched closely forhours he found a chance to slip away.

  Almost immediately the man discovered what had happened and pursued.By chance Frank fled out through a passage that led upward till thetop of the bluff was reached, but he fell and sprained his ankle, sohe was unable to get away. The hermit followed, and the mad battle forlife took place.

  "Well, this is amazing!" gasped Jack. "What are you going to do withthat treasure?"

  "Take it to some place for safe deposit and advertise for the legalheirs of Prof. Millard Fillmore."

  "And if no heirs appear----"

  "The treasure will belong to us."

  "Hurrah!"