Some days after the strange and exciting events just recorded, Peggy burst like a whirlwind into the little room,—half work-shop, half study,—in which Roy was hard at work developing a problem in equilibrium. It was but a short time now to the day on which they were to report to the navy Board of Aviation at Hampton Roads, and submit their aerial craft to exhaustive tests. Both brother and sister had occupied their time in working like literal Trojans over the Golden Butterfly. But although every nut, bolt and tiniest fairy-like turn-buckle on the craft was in perfect order, Roy was still devoting the last moments to developing the balancing device to which he mainly pinned his hopes of besting the other craft.

From the newspapers they had been made aware that several types, bi-planes, monoplanes and freak designs were to compete, and Roy was not the boy to let lack of preparation stand in the way of success. Detectives and the local police had been set to work on the mysterious plot whose object had been to entrap the boy. But no result had come of their work. Incidentally, it had been found, when the auto which Roy had driven to the deserted house was towed back for repairs, that the tank had been punctured by some sharp instrument.

As for the clue of the brilliant-studded comb, Peggy on examining it, declared it to be one of a pair of side-combs, which only complicated the mystery. Roy had thought of surrendering this clue to the police, but on thinking it over he decided not to. He had an idea in regard to that comb himself, and so had Peggy, but it seemed too wild and preposterous a theory to submit to the intensely practical police of Sandy Beach.

Roy looked up from the paper-littered desk as Peggy flung breathlessly into his sanctum. He knew that only unusual news would have led her to interrupt his work in which she was as keenly interested as he was.

"What is it, Sis?" he asked, "you look as excited as if the Statue of Liberty had paid us a visit and was now doing a song and dance on the front lawn."

"Oh, Roy, do be serious. Listen—who do you suppose has come back to Sandy Beach?"

"Not the least idea. Who?"

"Fanning Harding!"

"Fan Harding! The dickens!"

"Isn't it, and more than that, he is down at the Mortlake plant now. He is going to take up the Cobweb. And who do you think is to be his companion?"

"Give it up."

"Regina Mortlake!"

"Phew!" whistled the boy, "a new conquest for the irresistible Fanning, eh?"

"Don't be stupid," reproved Peggy, severely, "I've been thinking it over and I've just hit on the solution. Fanning, or so I heard, took up aviation when he was in the west. You know he always had a hankering for it."

"Yes, I recollect his fake aeroplane that scared the life out of you," grinned Roy.

"Well," pursued Peggy, not deigning to notice this remark, "I guess they decided that Mr. Mortlake would be a bit er—er—overweight isn't it called? so they sent for old Mr. Harding's son to manage the Cobweb at the tests."

"Jove, that must be it. Makes it rather awkward, though. Somehow I don't much fancy Master Fanning."

"As if we hadn't good reason to despise him. Hark! there goes the Cobweb now!"

A droning buzz was borne to their ears. Running to the window they saw the Mortlake aeroplane whiz by at a fair height. It was going fast and a male figure, tall and slight, was at the wheel. In the stern seat Regina Mortlake's rubicund aviation costume could be made out.

" Running to the window they saw the Mortlake aeroplane whiz by at a fair height."

"Fanning has certainly turned out to be a good driver of aeroplanes," commented Roy, as he watched; "see that flaw strike them! There! he brought the Cobweb through it like an old general of the upper regions."

Peggy had to admit that Fanning Harding did seem to be an expert at his work; but she did it regretfully.

"He gives me the creeps," she volunteered.

"There's nothing creepy about his aeroplane work, though," laughed Roy, "I shouldn't have believed he could have picked up so much in such a short time."

But a bigger surprise lay in store for the young Prescotts. That afternoon they had, as visitors, no one less than Fanning Harding and Regina Mortlake. While Peggy and the daughter of the designer of the Mortlake aeroplane chatted in one corner, Fanning placed his arm on Roy's shoulder and drew him out upon the veranda where Miss Prescott sat with her embroidery.

"I know you don't like me, Roy, and you never did," he said insinuatingly, "but I've changed a lot since I was in Sandy Beach before. Let's let bygones be bygones and be friends again. More especially as in a few days we'll be pitted against each other at the naval tests."

"Of course, if you are genuinely sorry for all the harm you tried to do us, I've nothing more to say," said Roy, "I'm willing to be friends, but although I may forgive, it's going to be hard to forget."

"Oh, that will come in time," said Fanning, airily, "I'm a changed fellow since I went west."

But in spite of Fanning's protestations Roy could not help feeling a sensation of mistrust and suspicion toward the youth. There was something unnatural even in this sudden move toward friendship.

"It's ungenerous, ungentlemanly," Roy protested to himself; but somehow the feeling persisted that Fanning was not to be trusted.

"How prettily you do your hair," Peggy was remarking to Regina Mortlake in the meantime.

She looked with genuine admiration at the glossy black waves which the other had drawn back over her ears in the French style.

"Oh, do you like it?" asked Regina eagerly, "I think its hideous. But you know I lost one of my combs and—but let's go and see what the boys are doing," she broke off suddenly, turning crimson and hastening to the porch. Once outside she plunged at once into conversation with the two boys, and Peggy had no opportunity of picking up the dropped stitches of conversation. She caught herself puzzling over it. Why had Regina been so mortified, and apparently alarmed, when she had announced the loss of one of her side-combs? Right there a strange thought came into Peggy's mind. The brilliant-studded comb that Roy had picked up! Could it be that—but no, the idea was too fantastic. In the pages of a book, perhaps, but not in real life. And yet—and yet—Peggy, as she watched the graceful, dark-eyed girl talking with splendid animation, found herself wondering—and wondering.

The next day, just as Peggy and Roy were starting out for a run to the Bancroft place, Fanning Harding and Regina Mortlake came whizzing up to the gate in the latter's big touring car—the one in which she had arrived in Sandy Beach. The machine was the gift of her father. It was a commodious, maroon-colored car, with a roomy tonneau and fore-doors and torpedo body of the latest type.

Beside it the Blue Bird looked somewhat small and insignificant. But Roy and Peggy felt no embarrassment. On the contrary, they were quite certain the Blue Bird was the better car.

"Where are you off to?" asked Fanning in friendly tones, while Regina bowed and smiled very sweetly to Peggy.

"Going to take a spin in the direction of the Bancroft's," said Roy, starting his car.

"What fun," cried Regina Mortlake, "so are we. Let's race."

"I don't believe in racing," rejoined Peggy.

"No, of course it is dangerous," said Fanning, "I guess Roy is a bit timid with that old car, too. Besides it's all in the way you handle a machine;"

Roy flushed angrily.

"I guess this 'old car,' as you call it, could give yours a tussle if it comes down to it," he said sharply.

Peggy tugged his sleeve. She saw where this would lead too. She saw, too, that Fanning was anxious to provoke Roy into a race. Presumably he was anxious to humiliate the boy in Regina Mortlake's eyes.

"Well, do you want to race then?" asked Regina, provokingly, her fine eyes flashing, "there's a bit of road beyond here that's quite broad and one hardly ever meets anything."

Now Roy was averse, as are most boys, to being thought a "'fraid cat," and the almost openly taunting air with which the girl looked at him angered him almost to desperation.

"Very well," he said, "we'll race you when we get to that bit of road."

"Oh, Roy, what are you saying," pleaded Peggy, "it's all a trick to humiliate us. The Blue Bird can't possibly keep up with their car, and——." But Roy checked her impatiently.

"You don't think I'm going to allow Fanning Harding to scare me out of anything, do you?" he demanded in as near to a rough tone of voice as he had ever used to his sister.

Poor Peggy felt the stinging tears rise. But she said nothing. The next moment the cars began to glide off, running side by side on the broad country road. Faster and faster they went. The speed got into Roy's head. He began to let the Blue Bird out, and then Fanning Harding, for the first time seemingly, realized what a formidable opponent he was placed in contact with.

As they reached the bit of road previously agreed upon as a race course, the banker's son stopped his machine and hailed Roy to do the same.

"Tell you what we'll do to make this interesting," he said, "we'll change machines. Or are you afraid to drive mine?"

"I'll drive it," said Roy recklessly, in spite of Peggy's quavered: "Say no."

"Good. That will give us a fine opportunity to compare the two machines," cried Fanning Harding.

He jumped from the bigger car and handed out his companion. Then, for the fraction of a minute, he bent, monkey wrench in hand, above one of the forward wheels.

"A bolt had worked loose," he explained.

"Come on Peggy," urged Roy, and against her better judgment Peggy, as many another girl has done before her, obeyed the summons, although an intuition warned her that something was not just right.

"Ready?" cried Fanning from the Blue Bird.

"All ready"; hailed back Roy, who found the spark and throttle adjustments of the maroon car perfectly simple.

"Then—go!" almost screamed Regina Mortlake. Peggy was looking at her at the moment, and she was almost certain she saw a look of hatred flash across the girl's countenance. But before she could give the matter any more thought the maroon car shot forward. Close alongside came the Blue Bird.

Motor hood to motor hood they thundered along at a terrific pace. The road shot by on either side like a brown and green blur.

"Faster!" Peggy heard Fanning shout somewhere out of the dust cloud.

Whi-z-z-z-z-z-z! It was wild, exciting—dangerous!

"Roy," gasped Peggy, "if——"

But she got no further. There was a sudden soul-shaking shock. The front of the car seemed to plough into the ground. A rending, splitting noise filled the air.

The car stopped short, and its boy and girl occupants were hurtled, like projectiles, into the storm center of disaster.