"Then we'd better be gettin' up in the air, so we can see what's going on," Jimmie replied. "I'd like to see where the motor car goes."

"We can satisfy our curiosity on that point without going up in the air," Ned answered. "The Vixen was left just over that cliff. There is a valley—a dent in the slope of the mountain—on each side of that elevation, and the Vixen and the motor car are in one of them and the Nelson in the other."

Jimmie started away on a run almost before Ned had finished speaking. In a few moments he was seen on the shelf, then he darted around the shoulder of rock and was lost to view. The popping of the motors continued.

Ned hesitated a moment, uncertain as to the advisability of leaving the machine in the sole care of the Indian, and then followed. When he gained the shelf on the opposite side he saw the Vixen slowly lifting in the air. The automobile stood above her, on the level yet treacherous spot where Ned had landed. In it were Thomas Q. Collins and the man he had seen in the automobile cap and goggles!

The Vixen did not look to be in good repair, just as Ned had supposed, for the newcomer had had only a short time to work over her, but for all that she was slowly leaving the narrow pit into which she had tumbled. Her motors were working, but did not appear to be doing any lifting.

Then Ned saw that a rope attached to the machine was doing the work. The motor car, moving very slowly forward, was pulling her up the steep acclivity, her rubber-tired wheels drawing and bounding against the rocks.

"If they get her up on that level space," Jimmie predicted, "they'll get her up in the air. You can see where they've been patching the planes, and the motors are workin' all right."

"What I'm interested in, just now," Ned said, "is that automobile.
I'd like to find the highway through which she entered that valley.
It must be through some tunnel, for there's no path over the
slopes."

"Then we'll keep out of sight an' watch," Jimmie observed. "See there!" he cried, as the wheels of the Vixen struck the level area. "She'll be in the air directly. One of the niggers is gettin' in!"

"What's that he's loading on?" asked Ned.

"Stones, as I'm a living boy!" he went on, excitedly. "Jump for the Nelson, kid, and get her into the air! You see what they are going to do?"

It was quite evident what the intentions of the others were. The
Indians were loading the Vixen down with sharp-pointed stones and
long wisps of dry grass; out from the nooks of the valley by
Collins, who had now left the automobile.

"We've just got to get the Nelson up in the air!" Jimmie cried. "They're gettin' ready to drop stones an' blazin' grass down on her planes. We've just got to get there before the Vixen sails over her!"

Stopping no longer to observe the motor car, or watch her course out of the valley, both boys dashed around the shoulder of rock and began working their way down into the place where the Nelson lay, with Pedro, all unconscious of the approaching danger, sitting in the driver's seat and wondering if he was ever going to eat again!

The whirr of the motors in the air soon told the sweating lads that the Vixen was rising from the ground. Just how they had managed to repair her so quickly was a wonder to Ned, but he had no time to consider that side of the case then.

"Do you see her yet?" panted Jimmie, as the two paused a moment on their toilsome way downwards.

"Not yet," was the reply, and Ned almost dropped a dozen feet and caught on the point of a rock which jutted out from the wall.

"Gee!" cried Jimmie. "That was a tumble! Got a good hold, there?
Then catch me!"

Before Ned could remonstrate the reckless little fellow had dropped. The impact of his body forced Ned from the crevice in which he clung, and together they rolled down a score of feet, bringing up in an angle from which a fall would have been fatal.

Ned came out of the tumble unharmed, but Jimmie lay like a rag in his arms as he straightened out and looked upward. The Vixen was rising over the cliff!

Ned drew his automatic and fired three quick shots in the air, but the aeroplane sailed on, apparently unharmed. In a moment she was directly above the Nelson, and Pedro was fleeing for his life.

Standing there helpless, with the unconscious boy in his arms, Ned saw the driver of the Vixen rain great stones down on the frail planes of the Nelson. Then a puff of smoke came from the driver's seat, and Ned saw that the wisps of straw were being ignited to finish the work begun by the rocks.

He fired volley after volley at the man who was doing the mischief, but he was so unnerved and excited that his bullets went wild. The crash of stones on the breaking planes sounded louder to him than did the explosions of his own revolver.

In a moment a blazing wisp of dry grass, or straw, dropped from the Vixen and sifted through the still air, the individual pieces of the bundle falling apart. Some of the little swirls of flame died out as the material passed downward, but others held, and dropped on the wounded planes!

Ned shouted to Pedro, ordering him to smother else incipient blaze with his coat, or anything the he could find, but the Peruvian was nowhere to be seen. Terrified at the movements of the aeroplane, he had hidden in the rocks.

Again and again the man on the Vixen lighted wisps of dry grass and hurled them down. Directly the planes were in a blaze. Ned laid Jimmie down on a narrow ledge and finished emptying his revolver, but to no purpose. He had never done such bad shooting in his life.

But Fate was abroad in the Andes that morning!

Presently the driver of the Vixen dropped his last wisp and shot upward, apparently not caring to engage in combat with the boy who had used him for a target so unsuccessfully.

As the aeroplane passed across the top of the valley, Ned saw a little tongue of flame on the under plane. The driver evidently did not understand his peril, for he mounted higher and drove straight to the north.

Ned watched the finger of flame grow as it bit into the fine fabric of the plane with something like awe in his heart. If the driver did not see his danger instantly and hasten down, nothing could save him.

While the boy watched, almost breathlessly, Jimmie stirred and opened his eyes. He had a bad cut on his forehead, but otherwise seemed to have suffered little from his terrible fall.

"Gee!" he cried, looking up at Ned with a grin. "I guess I took a drop too much!"

Ned did not answer. He was too busy watching the tragedy which was taking place in the air. Jimmie followed the direction of his eyes and caught his breath with a gasp of horror.

"He'll burn up!" he cried.

Both planes were now on fire, and the driver knew of his peril. It seemed to Ned that the fellow's clothes were on fire, too, for he writhed and twisted about as he turned the aeroplane downward.

"He'll get his'n!" Jimmie declared.

The Vixen came down almost like a shot, leaving a trail of flame and smoke behind her. Then the end came.

The charred planes gave way and the frame dropped, carrying the driver with it. They whirled over and over in the air as they came down. The fall must have been fully five hundred feet, and Ned knew that it would be useless for him to seek the man who had worked so much mischief to the Nelson with a view of doing him any service.

Below, the Nelson was sending up sheets of flame. Pedro now ran out of his hiding place and attempted to check the fire, but his efforts availed nothing.

"It is gone, all right!" Jimmie said, with a sigh. "Now, how are we goin' to get out of here? That's what I'd like to know."

"We'll have to get out the same way the others do," Ned replied.
"They have lost their aeroplane too."

"Yes," agreed the little fellow, "but they have a motor car, and we've only our shanks' horses!"

Ned extinguished the burning woodwork on the Nelson and made a hasty estimate of the damage done.

"The motors are not injured," he reported. "If we can get something that will do for planes, we can get her out."

"Then," said Jimmie, "I reckon it's me for the highway! I'll chase that automobile into where it came from. I'll bet I'll find cloth of some kind there."

"It might be better to send Pedro," said Ned.

"All right!" the little fellow agreed. "Then you and I can sleuth about this rotten country in search of gold! They say there's gold in these hills!"

The purr of the motor car's engines now came again, and Pedro hastened up the ledge and followed down into the valley where she lay. In a moment she was out of sight, and the Peruvian was moving toward a rift in the wall of rock to the east.

But Ned, watching from above, saw that there was only one person in the car. Mr. Thomas Q. Collins had been left behind!

"That's strange!" Ned mused. "Why should he remain here? What further mischief has the fellow in mind?"

When Ned returned to the machine he found Jimmie busy polishing the scorched steel work.

"All she needs is new planes!" the lad cried.

"Jimmie," Ned asked, "when you came here yesterday, did the Vixen follow you closely, or did she stand off and on, as seamen say, and take note of your course indifferently? What I want to know is this: Did the driver seem anyway excited when you speeded over this way?

"He followed tight to my heels," replied the little fellow. "Then, when he saw me land, he whirled about and went away."

An idea which seemed almost too good to be true was slowly forming in Ned's brain. Why had the Vixen always followed the Nelson? Why had she spied upon her without in any way interfering?

Again, why had Thomas Q. Collins been left there in the wilderness? Surely there were no accommodations in sight in those valleys—nothing to subsist on, no shelter from the weather.

He might, it is true, have remained out of a spirit of revenge, hoping to punish Ned for his treatment of him, but this explanation did not appeal to the boy. With the Nelson hopelessly out of repair, he could well afford to leave the lads to their fate, as the chances that they would be able to get out alive—being strangers to that country and, supposedly, to mountain work—were about one to ten.

And so, Ned reasoned, there must be some other incentive for the action taken by Collins. He had a subconscious impression that he knew what that incentive was, but hardly dared to whisper it to himself.

The boy's reverie was interrupted by Jimmie, who had been running back and forth in the valley in quest of wild berries, or something which would serve as food.

"I could eat a whale!" the little fellow shouted.

"Catch a hare and cook him," Ned suggested.

"The hares here are not exactly like our rabbits, but they are good to eat. If you go over into the little jungle below, at the end of this bowl, you might find one."

Ned, still wondering if what he hoped might be true, turned to the cliff which separated the two valleys and began a careful inspection of the rock formation. Away around to the east, under the shelf which ran like a terrace around the elevation, he came upon what he was looking for.

The shelf extended outward from the face of the rock, and under it, setting back into the cliff perhaps a dozen feet, was a cavern which looked out on the valley where the Nelson lay, but from which the machine itself was not in sight.

The floor of the cavern showed traces of human habitation. It had undoubtedly been occupied as a shelter from storms by mountaineers for centuries.

But the evidences of occupation which Ned saw were not those showing distant use. There was a tiny fire burning in a crevice which served as a chimney, carrying the smoke far up into the sky before discharging it.

Scattered about the fire were tin cans, some empty, some containing food of various kinds. Thrown over a heap of broken boxes in a corner was a coat—a tailor-made coat of fine material.

On a little ledge at the rear were a safety razor, a small mirror, and a shaving mug. Ned picked up the coat and thrust a hand into an inside pocket. That, he thought, would be an easy way to ascertain the identity of the owner.

In a moment he drew forth a folded paper, covered with figures in pencil. The figures were in columns, as if the maker had been setting down items of expense and adding them up. The total was in the millions. The calculations of a cattleman, covering shipments and receipts!

Ned continued his search of the coat and presently came upon a packet of letters, all enclosed in envelopes and neatly ticketed on the back. They were enclosed in a rubber band, and showed careful handling.

And the envelopes, every one of them, were addressed to Dr. Horace
M. Lyman, Asuncion, Paraguay!