CHAPTER VI.--ABOVE THE CLOUDS AT NIGHT.

The wind gained strength as the heat of the forest fires increased. The roaring of the gale and the heavy undertone of the racing flames effectually drowned the voice of the forester, and it was only by the motion of his lips that the boys knew that he was trying to talk to them.

Presently he threw his hands high above his head, weaponless, then lowered one and beckoned to them. Still keeping grasp on their revolvers, the boys approached him. His face was deadly pale, save for the glow of the fire which shone unnaturally on the wall behind him.

"This is no time for accusations," he shouted. "We must do something to check the fire."

"What is to be done?" Jack demanded, half won over by the apparent distress of the fellow.

"The blaze will burn itself out against the mountains," was the reply, shouted at the top of the speaker's lungs, "but the fire in the canyon must be checked by going on ahead and felling trees."

"Won't it burn itself out there, too?" asked Pat.

"I'm afraid not," was the shrill reply. "There is an opening from the top of the canyon to a valley in a fold of the hills. The fire will do incalculable damage if it passes through that."

"What do you suppose we can do against a fire like that?" demanded Pat. "An army could not stop the blaze now."

"You are mistaken!" shrilled the other. "Three choppers can clear a space which the fire will not cross."

"We'll get our axes and try," Jack said, reluctantly.

"Then make haste!" Greer shouted. "At all events we must leave this place, for the fire will soon be here. Come!"

When the boys turned to verify this statement they saw that the planes of the aeroplane were red with the reflection of the blaze below, and that the creeping fire was already showing at the lip of the plateau.

"The aeroplane is doomed, I guess," wailed Jack, and Pat thought he saw a look of satisfaction in Greer's face as the words reached his ears.

The smoke was now rolling over the plateau in great clouds, but through it Pat thought he saw figures moving from the south slope toward the aeroplane. Calling out to Jack, he sprang toward the machine, the suspicion in his mind that these were confederates of the alleged forester, and that the machine was, after all, the main point of attack.

Greer saw the movement and darted toward the boy as if to block his way, but Pat struck out viciously and turned him back. Then a bit of flame sprang up in the cloud of smoke which was sweeping over the plateau. It seemed to Pat that an attempt to burn the machine in advance of the arrival of the forest fire was being made.

When he darted forward again Greer caught him by the shoulder and hurled him away.

"Get your axes!" he shouted. "There is no time to waste here."

Then the smoke lifted for an instant and Pat saw three figures rise above the rim of the northern slope and hasten toward the aeroplane. Their arrival there was followed by shots and calls for assistance. Then the smoke shut down again, and the roaring of the flames drowned all other sounds.

Greer stood for an instant, braced against the wind, shielding his face from the hot blasts scorching the grass of the plateau, then turned and ran. Then both boys heard a call from the direction of the machine.

"The way is clear to the cavern!" were the words they heard. "Remain there until we return!"

"That's Ned," shouted Pat. "Just in time to save the aeroplane."

Almost before the words were out of his mouth there came a lull in the wind and the great machine ran forward a few yards, then swung into the air. At that moment Frank came running toward the two astonished boys.

"We've got to leg it!" Frank shouted, his mouth close to Jack's ear. "Drop low on the ground so as to get fresh air and run!"

Jack, although he had heard Ned's voice giving directions, and although he knew that Frank was by his side, could hardly sense the situation, or all that had taken place. The action had been so swift that he could not yet realize that Ned had snatched the aeroplane away from certain destruction and lifted it into the stormy sky in so short a time.

However, he did not stop then to place the events in neat order in his mind, for the fire was working across the scant vegetation of the plateau and the air was hot and stifling. It was all like a page out of the Arabian Nights, but he put the wonder of it away, grasped Frank's hand, and, crouching, ran toward the incline leading to the lake. There was safety there, at least.

Now and then, in their swift flight, the boys stopped and looked upward, hoping to learn something of the fate of the aeroplane, but the great machine was not in sight.

"Ned never can make it live in this gale!" Jack almost sobbed, when, at last, they all came to a halt at the margin of the lake. "The whole shebang will go to pieces and the boys will be killed."

"Aw, forget it!" grunted Pat. "I'm not in love with airships, but I know that Ned wouldn't have gone up unless he knew that he could handle the machine. He'll lift above the divide and drive straight before the wind. The good Lord only knows how far the gale will take him, but I'm betting my head against turnips that he'll come back by morning, asking why breakfast isn't ready!"

"How did you get wise to the trouble up here?" Jack asked of Frank.

"Why, I don't exactly know," the boy replied. "Ned sent me on ahead to look out for the aeroplane. He said he wanted to remain in the cavern and investigate. I was making slow progress up the hill when Ned and Jimmie came running after me. I had noticed long before that the sky looked like fires were burning somewhere."

"I should say so," Pat cut in. "The clouds looked like they had been soaked in red paint."

"When Ned came up to me, running like a racehorse," Frank went on, "he said he was going to take the aeroplane out, wind or no wind. I didn't have much chance to talk with him, but I understood that he was going to do just what Pat has suggested--run before the wind and swing back whenever he could."

"I presume Jimmie is good and scared by this time!" Jack commented.

"When we got to the machine," Frank went on, "we found two men there with some sort of torches in their hands, trying to set the machine on fire. We caught them unawares and left them lying there. I hope they didn't get burned to death."

There was a short cessation of speech while the boys listened to the roaring of the flames and watched the fire mounting into the sky. It was a wild scene--one calculated to bring terror to the breast of any human being. The wind was dying down a little, but the clouds were still driving fast before it, their edges tinged with flame so that they resembled golden masses floating across an eternity of space clothed in smoke.

While the boys watched the great display Frank pointed to a wall of flame rounding the corner of the plateau.

"The fire will burn this slope," he said, "and we've either got to get into the cave or out on the lake. Which shall It be?"

"The cave for mine!" Jack cried.

"And mine," echoed Pat. "Who knows what the fire will do to the lake?"

But Frank had had previous experience in the cavern. He was thinking of the still figure he had found lying there, and of the dark stains on the floor.

"If we could find a boat," he said, without mentioning his real reason for objecting to the cave, "we might get along very well on the lake. We don't know what stifling air we shall find in the cave, and, besides, the men we have just had a fracas with may return at any time. It wouldn't be nice to be locked up in that hole in the ground."

The wind was dying down to a steady breeze, and the fires seemed to burn lower. The clouds above were dark and threatening, save where gilded by the reflection from below, and seemed to be massing. Frank held up a hand and shouted.

"Rain!" he cried. "Rain!"

It was no gentle spring shower that opened upon the earth then. The fountains of the great deep seemed to have opened wide. The water fell in sheets, and in an instant the boys were wet to the skin.

"Better than fire!" Jack suggested.

The rain pelted down upon the forest fires viciously, and the hissing protests of the angry embers rose in the air. Through the thick veil of the rain clouds of steam could be seen rolling over the lake and along the threatened incline. In ten minutes water was pouring down the steep hill in sheets and the fires were leaping no more.

Pleased as the boys were at the opportune arrival of the rain-bearing clouds, they could not help wondering if the freak of chance which had preserved the forests of northern Montana had not brought Ned and Jimmie sudden death.

"They never can handle the machine in such an air-ocean," Jack declared, but the more optimistic Pat asserted that Ned must have been a mile above the rain clouds before a drop of water fell.

"I guess the fire brought this rain on," Frank said, wiggling about in his wet garments, "but it's just as wet as if brought about by some other means. What are we going to do now?"

"Why not go to the cave until the rain stops?" asked Pat.

"It is colder in there than it is here," Frank said, still thinking of the silent figure in the narrow tunnel back of the cupboard.

"We can't get any more water in our clothes and hides than we have now," Jack observed, "so we may as well stay outside and watch for Ned and the aeroplane. I don't believe any other person ever took an aeroplane up in such a storm. I'm afraid Ned was smashed against the divide."

"Ned's all right," insisted Frank. "Suppose we go back to the plateau and see if there's anything left of our tents."

"I'm game for that," Pat said, "but," he added, turning a keen gaze on Frank, "I'd like to know why you object to going to the cave. Jack and I would like to see it."

"Well," Frank replied, not without some hesitation at bringing the scene in the tunnel back to his mind in form for expression in words, "there's a crime been committed in the cave, and it's uncanny."

"A crime!" repeated Pat, all excitement at the suggestion of another adventure, "what kind of a crime?"

"A murder," replied Frank, with a shiver.

"Let's go in and see," Pat said.

"Frank's afraid," Jack put in.

"Of course I'm afraid," Frank admitted. "You go in there, and crawl on your knees through the thick air of a narrow tunnel, and put your hand on a dead man's face, and feel your other hand slipping in the blood on the floor, and you'll be afraid, too. I'm not going back there."

"We can stand here in the rain all night, if you want to," Pat said, with scorn in his voice. "Rainwater is said to be good for the complexion."

The wind was slowing down and the rainfall was not so heavy as before. The boys, Pat and Jack, joking Frank about his terror for the cave, and Frank just a little angry, began the ascent of the slope leading to the plateau.

"The rain saved the trees next to the mountain," Pat said, presently, "and if it checked the fire on the plateau at the same line our tents are all right. Say," he added, "who ever heard of such a downpour as that. I reckon the rain swept in from the ocean in heavy clouds which were broken open by the mountains."

"Much you know about it!" laughed Jack. "You talk as if you could cut a cloud with a knife."

"Anyway," persisted Pat, "the water tumbled out and checked the fires. Wonder what became of the man who said his name was Greer? He was standing in with the men who were trying to burn the aeroplane, all right enough, and I believe the whole circus was started just to destroy the airship and bring Ned's investigations to a close."

"We always do get into the thick of it at the first jump," Frank said, remembering the bomb under the cottage in the Canal Zone and the raid on the nipa hut in the Philippines. "Whenever we've got anything coming to us, we get it by lightning express."

"You bet we do!" Jack exclaimed. "Now we're getting a clear sky," he added, pointing upward, "and we're getting it short order time, too!"

The heavy clouds were gone, the moon was smiling down on the drenched earth, the stars were winking significantly toward a spot on the plateau where two unrecognizable figures, half burned away, were lying. When the boys reached the top of the climb and advanced to the spot where the aeroplane had stood they turned sick with the horror of the thing.

"I almost wish we had let them destroy the aeroplane," sighed Frank. "I don't like to think that these men came to their death through us. It is awful!"

"Did you shoot them?" asked Pat.

Frank shook his head.

"They shot at us," he said. "They fired as soon as we got to the rim of the dip, but missed because of the smoke and the wind. Then we rushed them, and they went down--to escape punishment, I thought--and so Ned got the aeroplane away."

"Then you had nothing to do with their death," consoled Pat. "They came here to commit a crime and were overcome by the smoke and heat."

Frank would gladly have accepted this version of what had taken place, but he could not bring his mind to do so at once. The horror of what he had found in the cave was still upon him.

Leaving the spot where what remained of the outlaws lay, the boys hastened to the wall of rock which terminated the plateau on the east. The rain had indeed saved the tents from destruction. The canvas was huddled against the wall, stained with smoke and heavy with rain, but in fairly good condition.

"We'll have to remain here, or about here, until Ned comes," Pat said, "so we may as well put the tents up. I wonder if it isn't most morning?"

"Does that mean that you are getting hungry?" grinned Jack.

"You bet it does!" was the reply. "Anyway, I'm going to see if I can find dry wood enough for a fire. If I can I'll make some hot coffee. Ned will see the fire, and know we are not in the cave."

Then an exclamation from Frank called the speaker's attention to the clear sky over the divide. The upper strata of clouds were drifting westward on a high current of air--what few clouds there were--and far up in the blue, the moonlight trimming the planes with silver, rode the aeroplane, seemingly intact, and working back on the high current toward the Pacific coast.