“FOR the love of Mike!” cried Bob Holton. “Whatever happened?”

“Plenty!” came from Joe quietly. “We had a fight.”

“A fight?” Mr. Wallace was perplexed.

“Yes, and a big one at that,” said Karl grimly. “But we licked them.”

“Licked whom?” demanded Bob, becoming impatient. “Come on. Tell us about it.”

Mr. Holton got to his feet.

“Look over there,” he directed, pointing to a spot near the tail of the monoplane.

Bob and Mr. Wallace looked.

Lying prone on the ground was a man, a native Colombian, evidently still dazed from a blow. He made not the slightest move, although it was apparent that he was not hurt seriously.

“Karl knocked that fellow out,” explained Bob’s father. “In addition to being a fine aviator, that fellow’s a fighter.”

Bob glanced at Karl. From the start the youth had believed the aviator could give a good account of himself if called upon.

“But that’s not telling us anything,” said Mr. Wallace. “What caused the fight? How did it all come about?”

“This way,” began Mr. Holton. “Joe and Karl and I were sitting in the cabin of the ’plane discussing the expedition when we were suddenly interrupted by a gang of at least five rough men, who rushed at the ’plane angrily. We didn’t know what their object in attacking us was, and never did find out. Perhaps they wanted to steal what we have, or they might have been in that crowd yesterday when we laughed and they thought we were making fun of them. At any rate they came at us furiously, and one man broke out the glass in a window. We got out of the airplane as soon as we could to defend ourselves. We couldn’t get to our guns because they’re in a nailed box. But we used our fists to good advantage and finally were able to beat them off. All got away but that fellow over there.”

“Well, of all things!” exclaimed Mr. Wallace. “Seems like we’re having trouble and then more trouble. Bob and I had an experience on the train that wasn’t very pleasing,” he said, and then told of the robbery in which he had lost a valuable watch.

“We’ll soon be out of this country, I hope,” sighed Joe. “Though I suppose it isn’t the country so much as it is our stroke of bad luck.”

“No,” agreed Bob. “Anyone——”

He stopped quickly, as he observed that the Colombian who had been knocked out was regaining consciousness. At first the man merely stirred about, as if totally unaware of what had happened. Then he glanced up and got to his feet.

Pausing but a moment to glare at the Americans, the man dashed away in the direction of the town, drawing his teeth back in a wicked snarl as he looked back at them one last time.

“I think we’d better get away from here as quickly as we can,” said Mr. Holton. “For all we know there may be another gang getting ready to attack us. The whole town might even come out.”

His remark served to set Karl Sutman to action.

“Let’s get the gas in the tank,” he suggested, walking over to the can that Bob and Mr. Wallace had brought filled from the city on the coast.

Together, Joe and the aviator lifted the heavy can up and poured out its contents. Then, after making the cap secure, Karl climbed in the cockpit and switched on the engine.

“This will take us from fifty to seventy miles—maybe farther, depending on how fast we fly,” he told the others, as they entered the cabin and snapped the door shut.

As they left the ground, Joe noticed that they were heading west. He wondered what was the meaning of this, since BogotÁ, which was south, was their goal.

“I’m going to find out,” he thought, and, stepping over to the transmitter, he put the question to Karl.

“I decided all at once to go over to that coast city—Cartagena,” the aviator answered. “There we can fill both our tanks to capacity and won’t have to worry any more. Otherwise, if we merely used the gas that Bob and Mr. Wallace brought, we might find it necessary to hunt up another town that has gasoline.”

“You think of everything,” praised Bob’s father, moving up to the transmitter.

“I’ve decided to make another change, too,” Karl said with a laugh. “I think it might be best to miss BogotÁ by a hundred miles and head at once for Lima, the capital of Peru. We can stop at Quito, the capital of Ecuador, for more gas, and then continue on to Lima. Here we’ll again land to fill our tanks. After that we’ll go on to—well, perhaps to Cuzco, if we want to look around a little before Mr. Lewis gets here by steamship. How does it sound?”

“O. K.,” said Bob quickly, and then, with a sudden thought, added: “How about the tank that leaks? Can we have it repaired in Cartagena?”

“Yes. That is, I’d think so. Why didn’t you and Mr. Wallace find out while you were there?”

“Upon my word, I never thought of it,” confessed the naturalist sheepishly. “And I’m sure Bob didn’t. But we could easily have inquired. After seeing the city, I’m inclined to think the tank can be repaired there.”

They found a little later that Mr. Wallace was right. At the first garage they entered, they were informed that the tank could be repaired.

It was necessary, however, for the garage man to take his welding outfit over to the monoplane, which was in a field quite a distance away. For this he explained he would be compelled to make an additional charge, but the others, knowing there was no other way out, did not object.

When the tank was mended and had cooled an hour or so, it was filled to capacity with gasoline. The spare was also filled, and then the explorers were ready to resume their journey.

A little crowd of people had assembled to see the monoplane off. They waved a friendly farewell as it soared high into the sky.

“Now I wonder if we’ll have any more trouble,” mused Bob. “Or will we have good luck and get to the Andes without much delay?”

Across jungle, plains, and hills they flew for well over an hour. Then they caught sight of something in the distance that thrilled them with delight.

“The Andes!” cried Joe joyfully. “At last we’ve seen the Andes Mountains!”

“I believe you’re right,” affirmed Mr. Wallace, straining his eyes to make out more clearly the series of distant bumps that were mountains.

As the explorers flew nearer, they could easily observe the high peaks and narrow valleys. At one time they flew directly over a short range of exceedingly lofty mountains.

The monoplane passed farther, and the towering slopes of the Andes became more prominent. They looked dark and forbidding, yet beautiful and romantic.

“It’s going to be dark before long,” said Karl, breaking the fascinating silence. “And as it isn’t wise to keep going over unknown territory, I’m going to land—if I can find a place.”

Picking out a level spot was very difficult, but finally Karl caught sight of a flat plateau stretching several hundred yards ahead. He brought the machine down as best he could, taking into consideration the difficulty of landing at high altitudes.

They did not pitch the tent that night, but curled up inside the cabin, too tired to use much more energy. By doing this they could lock the doors and spend the night in comparative safety. Otherwise, it would have been necessary to set a guard.

A heavy slumber overtook them and held them firmly until late next morning.

“Now to head for Ecuador,” said Joe, becoming impatient. “How long will it take us—to get to Quito, I mean?” he asked Karl.

“Let’s see. We’ve been about an hour out of Cartagena.” Karl pondered for a minute. “There’ll be about six more hours of air traveling before we get there. That is, if nothing happens.”

But nothing hindered their flight, and after a thrilling ride over fascinating country the explorers came to Quito, at the very rim of the lofty peaks. Karl finally was able to bring the airplane safely down at the edge of the city. He switched off the engine, and, with the others, turned to glimpse the surrounding mountains.

On all sides were the magnificent heights of the mighty Andes, reaching thousands of feet above the city. Quito itself was built in a wide valley, nearly eleven thousand feet above sea level.

All during the last hour, as they had soared steadily upward, Joe had had a strange feeling of nausea, which grew still worse after they had landed at Quito. Now, when they were about to make their way into the city, Joe slumped down on the ground beside the monoplane.

“I’m sick!” he moaned helplessly. “Guess I can’t go with you now.”