class="pnext">“Anyway,” went on Allan. “We found out that Joe had started south and your father wanted to warn you, so he sent us. And here we are.”

“Yes,” Terry broke in. “And Joe Arnold set down his plane at the Havana airport just a little while ago. I’m sure he saw us. Even if he didn’t he’d recognize Skybird. That man is up to mischief.”

“Do you think he’s going to try and make trouble for us?” asked Prim anxiously. “I’m afraid of that man, after what he did to you boys in Newfoundland.”

“We are not going to worry about it,” Terry announced with decision. “We are going to keep right on at the job we set out to do, and trust to luck to get us through safely.”

The four friends had an excellent breakfast with tropical fruits and delicious Cuban dishes. At times they forgot all about Joe Arnold and his threats to take away their father’s flying field. It was good to be together in this romantic city of Havana, and hard to realize that danger threatened them.

All about them were smartly dressed care-free people, spending money lavishly on the pleasures of the gay city. People came here from all over the world just to enjoy themselves.

But Terry would not allow them to forget that a difficult job lay ahead of them. It was necessary to push on. Consulting their maps, they laid out their route. The next hop would be across the open waters of the Caribbean to the landing field at Gracias a Dios in Honduras. That would be their next meeting place in case they became separated. Allan and Syd had planned to see them safely through the treacherous tropical weather of the Caribbean, before returning to Elmwood. Now that they were tipped off to the fact that Joe might make trouble, Terry could be depended on to keep her eyes open and avoid him. But the boys decided they would watch Joe and find out what he was up to.

The weather reports were favorable. There was always the warning to watch out for sudden storms that were common over the Caribbean.

Their take-off was delayed by Terry insisting that her engine was not working properly. Allan came alongside to listen as she warmed up the motor. “Why it sounds all right, Terry. I don’t hear anything wrong,” he said.

“But listen!” shouted Terry. “Listen to that rough hum.”

“You’re right, Terry,” said Allan as the girl shut off her engine and got out. Slipping into her overall suit, she started to work.

“Has anyone been near my plane?” asked Terry of the young mechanic whom she had warned.

“No. That is nobody touched it. There was another flyer who stood around admiring it and asking who you were. He even wanted to know where you were going. Then he said he’d like to take a look at your engine to see what kind you had. But I didn’t let him stick around,” replied the youth. “I told him to clear out!”

Allan and Terry got to work without waiting for further explanation. A full hour went by before they had the engine humming smoothly enough to suit the trained and sensitive ear of Terry Mapes.

Once more they were ready to take off. Terry taxied over the long field, making sure that the engine was working properly before she pulled back on the stick and sent Skybird nosing into the brilliant blue sky.

Terry’s heart was beating with happy excitement. The take-off never became a commonplace occurrence to her. She thrilled as she felt the ship lifting from the ground and in the face of the wind, rising to dizzy heights above the earth.

Allan and Syd followed and for half an hour they flew at about the same altitude. Then Allan lagged behind and rose above them to a height of five thousand feet. Both flyers were watching the sky behind them to make sure that their enemy was not in pursuit.

Joe Arnold had put in a busy morning in Havana. Here was where he had some shady business that would give him the ready money for taking up the option on the Dick Mapes Flying Field. And when he started out half an hour after the other planes, he flew high and well out of sight.

Terry and Prim were content to fly at about two thousand feet. They were enjoying the view of the southern sea dotted with islands and failed to see the pursuing plane, high above them in the distance.

But Joe Arnold was watching intently every move of the two planes, and the cold, menacing light in his eyes was a threat against these young flyers who dared to upset his plans, and keep him from realizing his ambition.

His mind was working fast. At the next flying field, he would have a show-down with them. His business deal in Havana had not been successful. It would be necessary to return to that city once more before he got the money. Joe Arnold did not know just what kind of a show-down he would have with these girl flyers. He would leave it to chance and his usual good luck unless he could think of some plan as he flew through the blue sky. Up in the clean air of the heavens this man was planning to destroy them.

But Terry and Prim, unconscious of his plans, were watching the changing colors of the islands, then faced once more the open sea toward Honduras.

CHAPTER III

Tropic Storm

High above the sapphire mirror of the Caribbean, Terry kept her plane in a southwesterly course. The sun was a pitiless ball of flame that sent out long fingers of fire. It was tropic weather.

Above them Allan’s plane was soaring ahead now. The sight of Joe Arnold at Havana had made them fear an attack, and the four flyers were watching to see whether a third plane was following them.

Leaving the islands behind they flew out over the sea, a great expanse of deep blue and purple water.

Suddenly Prim called to her sister. “Look Terry, there’s land over there, away to the left.”

“Yes, I see,” answered Terry. But she was watching the horizon with anxious eyes. That dark purplish mass looked to her like a low-lying cloud. There was something unnatural about it. Its color was changing rapidly to a reddish hue.

“I don’t like the looks of it, Prim,” called Terry. “See how the light is changing.”

A reddish haze had spread over the whole sky, the sun appeared like a great disc of hot metal. The sight was weird and menacing.

“What’s the matter, Terry? Is it a storm?” Prim asked.

“Yes, a tropic storm. We’ve got to race it. Where are the boys?” Prim leaned over the cowling and strained her eyes to the sky, but that strange and terrifying haze had blotted out the other plane. Terry circled and banked in an effort to find their friends. Then, opening the throttle wide, the girl sent her plane straight before the storm. It was her only chance. If she could out-race that storm, she would be saved.

Sending her plane ahead and in a gradual rise, the girl tried to get above the haze. These tropical storms often covered only a small area,