the cockpits, they heard a shout and their new friends came hurrying to the field to bid them goodbye.

Prim was glad they had come. She wanted to show off her quiet sister who always got her plane into the air so gracefully, and her face glowed with pride as Terry taxied across the field, swung around and headed into the wind for a good take-off. Skybird took to the air like a great bird and under Terry’s guidance circled the field several times for the benefit of their friends, then headed out over the Atlantic, flying south.

They did not know that a plane had been set down on the field half an hour before. The pilot had recognized Skybird and kept well out of sight. As he watched the girls from the shelter of the hangar, his face expressed the hatred and treachery that he felt.

It was Joe Arnold, their father's business rival and dangerous enemy!

“What are those girls doing here? Do they imagine they can fly to Peru and see Peter Langley?” thought Joe to himself. He made up his mind that the girls would never reach Peru. He would stop them, somehow. He must do it.

Joe Arnold frowned. As his plane was more powerful than Skybird, he could easily out-fly them and reach the mine a day before they could do so. But, first, he had some mysterious business to attend to before he would have the money for the option. Meanwhile he must do something to prevent the Mapes girls from continuing their trip until he was ready.

Before Skybird had disappeared in the clouds, Joe Arnold had left the field and was following after that tiny speck in the sky, trailing it relentlessly.

The next stop was Miami, and here again the girls made a thorough inspection of their plane. From now on their way would be over the Caribbean, where storms might spring up without warning. Skybird must be in perfect form. And when Terry finished her inspection, the little plane was ready for the hop to Havana.

The girls congratulated themselves that everything was going along well. They were even a few hours ahead of their schedule and Terry’s face was glowing with happiness and excitement. Ahead of them was the Caribbean. She had often dreamed of making this flight over tropical waters and now she was really here.

Below her were the keys and reefs of the Florida coast spread out flat on the blue water. They were like a painting in delicate pastel shades. Crossing the line of the reefs, Skybird headed boldly out to sea. Prim watched the smooth water, fascinated by the patterns made by steamers as they cut through the water, leaving an ever widening wake behind them. She felt safe, knowing that their amphibian plane could land on the water and float.

Terry sighted the coast of Cuba first, a delicate outline seen through a haze that dimmed the view and gave it a fairy-like appearance. Soon they sighted the grim old Morro Castle, the Spanish fort, and as they came nearer and flew above it, they could see the broad avenues of the lovely city of Havana. The marble capitol was dazzlingly white in the sunshine and the colored roofs of the houses, as seen from the air, arranged themselves in a fantastic design. It was a city of gay pleasure.

Terry brought her plane down at the Havana airport with a sense of relief. The first lap of that journey was over now.

A few minutes later she was handed a telegram which read: “Allan and Syd will join you at Havana. Wait. Dad.”

Terry’s eyes blazed for a moment. “What do you think of that, Prim? Allan and Syd are coming here. We’re to wait for them! I’ll say that’s nerve! Dad thinks we can’t make the trip without the help of the boys.”

“That’s nonsense, Terry! Dad knows we’re equal to it. The boys probably want a holiday and are coming just for the fun of it. I’m going to be real glad to see them. The more the merrier, I say,” replied Prim.

“I’d be glad to see them if I thought that their trip was not just because they think that we have to be looked after,” declared Terry. “I want to make this flight without help from anybody.”

“Don’t get too independent, Terry. It doesn’t pay,” her sister cautioned her. “But right now let’s go and get some breakfast. I’m starved.”

After they had finished with the customs and entry regulations the girls started toward the restaurant. A plane was circling about their heads looking for a landing.

Suddenly Terry grabbed her sister’s arm. “Oh Prim, look there! It’s Joe Arnold!”

“Where did he come from? What’s he doing down here?” demanded Prim, as if her sister knew all about Joe Arnold’s affairs.

Terry laughed nervously. “Ask me something easy! But of one thing we can be sure. Whatever it is that has brought Joe Arnold down here, it’s bound to be crooked, whether he is on business of his own or just trailing us. That man couldn't be decent!” Terry said with indignation.

“What are we going to do, Terry?” asked Prim.

“We are going to do nothing at all, except keep our eyes open,” answered Terry as she slipped back to the hangar and spoke to the mechanic who was looking over her plane. She gave him her sweetest smile as she spoke to him. “Keep your eye on my plane. Don’t let any stranger near it.” And she gave him a five dollar bill.

The young man promised and as Terry turned away he smiled to himself. “Guess she’s new to the game,” he thought. “Afraid someone will want parts of her plane for souvenirs.”

“Come on Terry, hurry. If you only knew how hungry I am!” cried Prim. But now another plane had approached and made a neat landing.

Prim stopped short and grabbed her sister’s arm. “Oh Terry,” she cried, “I’m almost sure that’s Allan in his new plane.”

“You’re right. That’s Allan! And Syd is with him!”

A few minutes later Allan and Syd leaped from the cockpits and were waving to the girls with whoops of delight. Terry and Prim hastened back across the field to welcome them.

“Hurry up!” cried Terry. “Prim is starving!”

“She’s got nothing on us,” Sid answered. “We could eat our shoe strings,—almost!”

When they were all seated at breakfast, Terry suddenly turned to ask Allan, “What’s the idea of trailing us down here? Are you taking a vacation?”

“A sort of vacation,” answered Allan. “About an hour after you left the other day, Syd and I got home. We finished up our business in half the time we expected. Then we heard some reports. Joe Arnold had been back at the field and was bragging around that he was starting out to make the final deal with Peter Langley for your father’s flying field. He sent notice to your father to vacate the field.”

“Why the nerve of that man!” cried Terry. “He’ll do no such thing! I won’t stand for it!”