Dick Mapes could never find a flaw. Terry knew her job.

Bennett Graham had all the necessary legal papers ready and a certified check to close the deal, so there would be no hitch at the last minute. These papers were carried in a small brown leather case and sewn into the lining of Terry’s flying coat.

Prim loved stylish clothes and her white flying suit was smartly cut. Terry turned to admire her pretty blonde sister just before they were ready to hop off.

“What’s the idea of that necklace?” said Terry with a laugh. “Girl flyers don’t wear necklaces with bright red jewels.”

“Don’t they? Well, this one does! It just suits my fancy, Terry Mapes. I think it looks smart, it adds a bit of color to my white costume.”

“All right, Prim, just as you say. Now, is everything set? How about your sweet tooth. Got plenty of cake chocolate?” teased Terry, for Prim was always nibbling at something sweet.

“Sure, my pockets are full. Here put this little package of crackers in your coat. We may get hungry as we fly along. And I’ve put up a big lunch in case we need it.”

At the last minute Prim adjusted the harness of the parachutes about Terry and herself not minding her sister’s impatient shrugs of disdain.

For some reason Terry was always impatient of parachutes. She felt like an amateur even though she knew that many of the big flyers never went up without putting one on, as a safeguard in case of accident.

Terry looked with satisfaction at Sally Wyn, the little waif they had brought with them from the far north. The girl was fluttering about the field like a butterfly. She seemed to be in half a dozen different places at the same time, running errands and making herself useful. With Sally there, her father and mother would not be so lonely. The little orphan had found a place in the hearts of Dick and Alice, and they would not hear of her leaving them to go to work. With her happy disposition she kept the household filled with laughter. Alice often wondered how she had ever been happy without this fun-loving girl. And she had a way of making Dick forget that he was a cripple. She amused him.

As the girls said goodbye to her, Sally called out: “Next year Terry Mapes, I’ll race you to Peru!”

It was a glorious morning, the sun was just rising as Terry sent her plane into the air and headed south. There were no last minute delays.

Now it remained for Terry and Prim to reach Peru, find old Peter Langley and convince him that he was mistaken and make him want to sell Dick the property. And in Terry’s mind there was no doubt that she could accomplish it.

Below them was a vast stretch of fertile country with streams, lakes and broad green valleys. And high in the air, Terry's hand at the controls felt the spring of her little plane and was certain that Skybird was thrilling at the adventure.

Terry held the plane down to a steady speed, hour after hour, only changing the monotony by diving to a lower level or rising to greater heights. They were following along the general line of the airway. They could pick out the landing fields and see the position of the great beacons that would flash at night to guide the flyer to the hangars on the ground.

Terry and Prim had decided to stay all night at the Waverly Field, far to the south. That meant steady flying all day, only coming down to refuel at long jumps.

They saw the lights of the Waverly Field a full half hour before they expected to be there. “Shall we go on?” asked Terry through the earphones. “We can easily reach the next landing field before dark.”

“No, let’s stay here. You look tired and besides I like the looks of this pleasure beach,” replied Prim.

Terry put Skybird into a steep spiral, leveled and circled the field and then put the plane neatly down on the ground.

Little did the girls think as they were greeted by the manager of the flying field that this was where their troubles would begin. That before they reached Peter Langley’s mine they were to face an enemy who was desperate with greed and hate. And that at times the girls would despair of escaping with their lives!

CHAPTER II

Pursued by a Flying Foe

Waverly was a popular beach resort and Prim was delighted to see that there was a pleasure pier which was gaily lighted up.

She cried, “Oh, Terry, it looks as if there might be dancing down there. Let’s hurry to the hotel and change to our party clothes.”

“Prim Mapes, you promised me that you wouldn’t take any party dresses this time. You said we’d be just girl flyers with no excess baggage,” retorted her sister.

Prim laughed. “I tried to Terry, but I couldn’t leave out our new frocks. I was certain we’d run into some sort of entertainment where we’d want some pretty dresses.”

Terry looked her disgust. “But Prim, I don’t even want to dance. What am I going to do with these documents while I’m dancing?”

“You could leave them at the hotel in the safe,” answered the easy-going Prim.

“Just forget that, Prim. Wherever I go, these papers go with me. If you insist on dancing I’ll have to go along, but I'll have the papers on me.”

As the girls talked over their plans they arranged for the care of their plane for the night and for refueling, as they intended to take an early start the next morning. Then they went to the hotel where many summer guests were staying.

Prim made friends easily and by the time Terry had registered for them at the desk and made arrangements for getting away early the next morning, Prim had a group of girls around her and was laughing and joking with them as if she had always known them. Terry envied her sister this ability to get acquainted with people at a moment’s notice. It would have taken her a week, at least, without Prim to break the ice, to become friends with these strangers.

When the two girls came down to the dining room half an hour later, their new acquaintances hardly recognized them. Prim was dressed in a fluffy gown which made her look like a lovely bit of Dresden china. Terry was very boyish and trim in her sports dress. She had an aristocratic manner, attracting notice by her very aloofness.

The dancing pavilion was built out over the water and they could hear the surf breaking about the pier. Prim danced to her heart’s content, for partners flocked about her. But Terry was uneasy for pinned to her slip were the valuable papers she must deliver in Peru. She was relieved when Prim finally consented to go back to the hotel, exchanging addresses and promising life-long friendship with her new friends as she went along.

At the first flush of dawn, Terry and Prim were at the hangars preparing to take off. Terry made a careful check-up on her plane to see that everything was in order and as they were about ready to climb into