Knowing little of the actual working of aeroplanes, Mary did not realize what the stopping of the engine meant. She thought Tom had simply shut it off, as he often did, so the noise would not interfere with their hearing of what was going on below.

“Go on back up, Tom!” cried the girl. “I don’t want to go so close.”

“I’m afraid there’s no help for it,” stated Tom grimly.

“What—what do you mean?”

“I mean the motor’s stopped. Something has gone wrong with it. We’re making a forced landing. Goodness knows what the outcome will be!” But Tom said the last to himself as he saw the forest fire seemingly rushing nearer and nearer.

It looked as if he would crash down in the midst of the burning trees.

“If there was only an open place to land it wouldn’t be so bad!” desperately thought Tom. “I might be able to make it. But to crash down into a lot of trees and bushes, and with those trees and bushes on fire.”

Still he kept up a brave front for Mary’s sake. It was more on her account that Tom was worrying than on his own. He felt that he could take a chance and jump at the last minute, though he carried no parachutes on this plane. But for Mary to leap was out of the question.

“Oh, Tom!” she cried, “what is going to happen?”

For a moment the young inventor did not reply. Then a desperate idea came into his mind. It was a big chance, but the only one, and it must be taken.

Not far away was Lake Carlopa, a large sheet of water on which Tom had tried out many of his marine ideas. If he could reach that he might yet save himself and Mary, and, perchance, even the plane. For though the Hummer was not equipped with pontoons for alighting on water, yet the plunge into that element would be less damaging to her than a crash to the ground.

“And there’ll be a chance for us, too,” thought Tom. “She’ll keep afloat on her wings for a few seconds if she doesn’t go into a nose dive. Yes, I’ll head for the lake.”

Desperately he tried to picture to himself the grounds surrounding the lake. He was trying to decide whether there was a field big enough in which to bring the Hummer to a regular gliding landing. If there was, nothing more would happen than always happened when an aeroplane landing is made.

But, as Tom recalled it, there were only scattered farms about the lake, and none of these was suitable for a landing field. Adjacent to the lake were picnic grounds, but these were covered with scattered trees and buildings.

“The open lake is my only chance,” decided Tom. “But can I reach it? That’s the question.”

He could see, shimmering in the sunlight ahead of him, Lake Carlopa. But he also became aware that his machine was steadily going down. He tried to figure out whether he could gain enough horizontal distance in proportion to his vertical drop to make the lake. And as he looked at the distance separating him from the body of water, it was with a sinking sensation in his heart that he answered himself in the negative.

“It can’t be done!” Tom told himself.

This being the case, he must pick out the next best expedient.

“We’ve got to crash, and soon,” he reasoned. “I’d better pick out a big, soft tree. The upper branches will give a little and bring us up gradually. A tree’s better than the ground with its underbrush.”

After her first spasm of terror Mary had become calm, and was sitting tensely in her seat waiting for Tom to bring her out of the danger.

It was not the first time she and the young inventor had been in desperate plights, and always before this Tom had come out ahead of the game in taking chances with death. Of course there could be one last time, but Mary was not thinking of that.

“It looked as desperate as this on Earthquake Island,” she told herself. “Yet we got off, thanks to Tom.”

All this while the Hummer had been gliding down on a long slant. Mary realized, of course, that the longer and more gradual the slant, or angle, at which the falling aeroplane approached the earth, the better chance it had for making a gentle and safe landing. It is the sudden nose dives, or tail spins, straight to earth that crash the planes and kill the pilots.

Tom was saving his machine. He would let it glide swiftly down for a short distance and then head it up, so it would nose toward the sky. This would slacken its speed and also carry it further along.

But it was evident that he could never cross the wide area of the burning forest and reach Lake Carlopa. That was out of the question. The next best thing, as Tom had decided, was to land in some big tree, the springing branches of which would act as a cushion.

“But I’ve got to pick out a spot where there isn’t any fire,” Tom told himself.

There was, of course, a certain burning area of the forest fire. Equally of course, there was not an even number of square miles ablaze. The fire was irregular in shape, and there were portions, perhaps a mile in extent each way, where the flames had not taken hold. Also, because of the nature of the fuel on which it fed, the fire advanced irregularly. The line of its advance was one that curved in and out, so that there were indentations here and there like the shore line of the sea, with bays of fire and points of woodland as yet unburned.

To pick out one of these places was Tom’s desire, and as the aeroplane glided nearer and nearer to the earth he knew that he must soon make this decision.

“Oh, Tom, what are we going to do?” faltered Mary. The suspense was telling on her. She could not quite fathom Tom’s object.

“We’re going to land in that big pine tree,” he suddenly exclaimed. “Hold your arms over your face, Mary, so you won’t be scratched. Look out now—here we go!”

As Tom spoke he ducked down behind the protection cowl of the cockpit in front of him, having a moment before adjusted the steering lever so as to glide into the top of an immense pine tree which stood in the midst of a clump of other giants of the forest, in a space as yet untouched by fire.

A moment later the Hummer crashed—crashed with a thud, a rending, a crackling, a splintering and tearing that went to Tom’s heart, for the plane was almost like a live creature to him.

Even as the plane crashed, Tom knew that he had made the best landing possible, and that, for the time at least, he and Mary were safe.

As Tom had anticipated, the spreading branches of the great pine tree acted as an immense cushion, and as the Hummer was a comparatively small plane, she was buoyed up. That is, at least long enough to take up the first shock.

In a few seconds Tom realized that he and Mary must make a hasty exit from the plane, for it might slip from its position, and portions of it drop on them as they slid from their seats.

The poor Hummer was badly broken. A plane cannot crash down into a tree and not have something like that happen. They are not built for that sort of thing. Tom realized this.

“Quick, Mary!” he called. “Unstrap yourself and I’ll help you climb out and down. I don’t know how long this plane will stay here.”

Mary had recovered her nerve after the first shock of the crash and as soon as she realized that neither of them was hurt beyond more than bruises and a shaking up.

“I can get out myself,” she announced, as she loosed the strap that held her to the cockpit seat. “And I can climb down out of the tree, Tom. I’m glad I wore leather knickerbockers to-day.”

“So am I,” murmured the young inventor.

He had loosed himself in his seat and turned now to help Mary, but of this there was little need, since she was capable of acting for herself.

Several of the branches of the great pine had been broken off, and the jagged ends were sticking through the frail wings and the almost as frail fuselage of the plane. These branches thus held it in place for a time, but it might slip down at any moment.

“How are you making it, Mary?” asked Tom, as he climbed out on a branch.

“I’m all right,” she said. “This is fun—just climbing down out of a tree,” and her laugh showed that her nerves were in good shape, for which Tom was glad. But then, Mary Nestor never was the sort of girl to go off in a faint. She was a brave girl, and that was why Tom liked her so much.

Together the two made their way down out of the pine tree, leaving the plane impaled on the branches over their heads.

“Poor Hummer!” murmured Tom, with more feeling than he cared to show.

“Yes, and poor us, too, perhaps, Tom!” exclaimed Mary.

“Why, we’re all right!” he exclaimed, as they reached the ground. “Hardly scratched.”

“Yes; but look! The fire! It’s all around us!”

Then Tom realized the peril he had all but forgotten—the peril of flames. As Mary spoke, the fire, with a sudden burst, leaped a gap hitherto open and the young people were in the midst of a raging conflagration—blazing trees and bushes all about them!

Mary Nestor had borne up bravely during the previous trying experiences. But the discovery that the fire was all about them unnerved her and filled her with horror.

“Oh, Tom!” she cried wildly. “We’re doomed! If we only could have stayed up in the air!”

“That couldn’t be done,” Tom said grimly. “We were lucky enough to get down as we did without being hurt.”

“Yes, I know. But now, Tom, look!”

Shuddering, Mary pointed to the encircling and advancing flames. As yet no clouds of smoke had blown their way, but it was only a question of time when the choking, acrid fumes would almost smother them—blind them.

“There must be some way out!” muttered the young inventor.

Desperately he scanned the ever-narrowing circle of fire about him and Mary. What could be done?

Dry as the woods were for lack of rain, yet the trees and bushes were green, and burned in a certain, slow way which alone might prove the salvation of the two. Had this been fall, with a mantle of dried leaves on the ground, the fire would have flashed through as though igniting gunpowder. As it was, the closing in of the ring of fire was gradual. This, at least, gave Tom a chance to search his mind for some way out.

He gave a last despairing look up into the tree where hung the wreck of the Hummer. Truly, if the crash had not destroyed the little machine beyond hope of repair, the flames would soon finish her. But Tom was not a youth to sigh long where it did no good. His chief concern must now be to save Mary and himself.

“We’ve got to get out of this!” he cried. “It will soon be too hot for us.”

“But can we get out?” Mary’s lips were white, but she now had control of herself.

“I think so,” Tom replied. “While it looks as though there was a solid ring of fire about us, there must be breaks in it here and there—places where there is comparatively bare ground, big rocks and so on, that will make a passageway for us. We must try to find one of these places, Mary. Now follow, but keep right behind me.”

Tom said this because he wanted to be prepared to save Mary should a sheet of flame suddenly spout up in front of them.

“Wait a minute!” cried the girl, as Tom would have made a dash toward a place where the smoke and fire seemed less dense and fierce.

“What’s the matter?”

“Can’t we use these? Wrap them about our hands and faces in case we get too near the fire?” asked Mary.

She pointed to two closely woven woolen blankets that had fallen out of the forward cockpit of the Hummer. Tom had stowed these away to be used on occasional trips when he went up to such an altitude that it was very cold, and a blanket about his legs and those of his passenger might add immeasurably to their comfort. With the tilting of the plane the blankets had fallen out shortly after Tom and Mary had climbed down from the tree.

“I’ve often read of persons wrapping their head in wet blankets to pass through flames,” said the girl. “And these two are wet, Tom, look, sopping wet.”

“Be careful they aren’t soaking in gasoline!” warned the young man, as Mary picked up the coverings. “I guess that’s what happened—the gas tank sprang a leak.”

Mary’s answer was to raise one edge of a blanket to her nose.

“It’s water!” she cried. “Not gasoline at all.”

“Good!” exclaimed Tom. “The radiator burst, of course, and soaked them. Good enough, Mary. They will be just the thing to protect our heads and faces. It’s mighty dangerous to breathe smoke-laden air. Now we’ll have a better chance!”

He saw to it that Mary had the wetter blanket of the two, then, with the coverings held in readiness to use should they approach too near any flame, the two in such a desperate plight started in that direction where the flames and smoke seemed least thick and menacing.

All about the girl and the youth the fire was raging. There was no difficulty now in hearing the crackling of the flames or the crash as some big tree, burned through, fell in the path of the raging element. Tom listened, thinking he might hear the shouts of the fire-fighters, and it was his hope that they might come to the rescue.

Though there might have been men and boys near the two imperiled ones, their presence could not make itself known above the roar and crackle of the flames.

For a time it seemed as if Tom and Mary might win through to safety by keeping on in the direction they first took. They went on for some distance, now and then stopping to let what wind there was blow aside a curtain of choking, blinding smoke.

So far had they progressed that Tom was on the point of calling: “I think we’re going to make it, Mary!” when, almost as he spoke, a curtain of smoke was swept aside and they saw a line of flame directly in their path over which it was impossible to leap and through which it was certain death to pass. Hitherto they had jumped several little, low lines of fire, which were low because they had little on which to feed.

But this ahead was part of the main blaze, and it needed only one glance at it to tell Tom and his companion that further progress was blocked in that direction.

“No go!” gasped Tom, shutting his eyes a moment to ease the smart and burn caused by the smoke.

“I should say not!” agreed Mary. “Suppose you go down that way and try a little to the left. It doesn’t seem quite so smoky there.”

Tom looked, and was of the same opinion.

“Better put the blanket over your head,” he told the girl. “It seems to be getting hotter and more sparks are falling. They might catch in your hair.”

The thickly woven blankets, wet as they were with water from the broken engine radiator, would prove a good protection against sparks.

Accordingly, Mary threw hers over her head and Tom did likewise. Then he dashed in the direction the girl had indicated. But they did not get as far along this trail as they had on the other before they were stopped by a wall of fire.

“Oh, dear!” sighed Mary. “What are we going to do?” She felt helpless and almost hysterical, but for Tom’s sake, resolutely held herself in control.

“Got to try some other direction!” gasped Tom, opening the blanket around his face a little so he could breathe more freely. “We’ve got to get out!”

Apparently, the only other course was to retreat and try the right, thought Tom, since the left had proved impracticable. And it was this decision—the only one possible under the circumstances—which eventually saved them.

No sooner had Tom taken the lead and gone a few steps down what seemed a fairly well defined path than he gave a shout of exultation.

“What is it?” cried Mary. “Do you see a way out? I don’t. The smoke seems thicker than ever!”

“It is,” Tom said. “But we’ll soon be all right. I know where I am now. I know it by that big rock. A little way down this path is a cave. It’s near a brook, and though the brook may be dried up, the cave will make a place in which we can be safe from the fire. It’s always damp in that cave. Besides, there’s nothing in it to burn. Come on, Mary!”

“Are you sure you’re right, Tom? It looks worse than ever in that direction!”

“Yes, I know where I am now,” he replied. “We’ll soon be all right!”

Though Tom spoke positively, Mary had her doubts, especially as it got hotter and smokier as they went down the path and the crackle of the flames was louder.

But once Tom Swift had been in a certain place, he never forgot it. He had an excellent sense of direction, and his memory had not played him false on this occasion.

Running along the edge of a tract of brambles and briars that were beginning to burn fiercely and looking back to see that Mary was following, Tom led the way down a little gulch. He seemed to be going right into the heart of the flames, and had Mary not known him as well as she did she might have feared to follow.

But she kept on, and a little later Tom came to a stop at the edge of a black, yawning hole in the side of a hill.

“Here’s the place!” he cried. “And there’s the brook! Some water in it, too, which is the best luck yet. We’ll have time to wet the blankets and get a drink! My mouth is parched!”

Mary, too, suffered from thirst, but she had made up her mind not to say anything about it for the present. Now, however, that there was a chance to get a drink, the thirst seemed to rush upon her irresistibly.

The fire had not yet reached the little gully, but the trees and bushes on the top of the ridge beneath which extended the cave were starting to burn.

“We’ll have a few seconds,” Tom remarked. “Come on down to the brook.”

In spring, following the rains and the melting of snow, the brook was of goodly size. Now it was much smaller, though Tom knew it widened and deepened about half a mile farther down.

The two laved their hands and faces in the cooling water, drank copiously of it, and then soaked their blankets well. Then, as a fiercer crackling of flames than any yet warned them that the fire was advancing, Tom cried:

“Come on!”

Up from the edge of the brook they ran and into the cool, dark and friendly shelter of the cave. They reached it only just in time, for they were no sooner inside than a shower of sparks and burning brands, falling into some dry sticks, leaves and grass near the mouth of the cavern, sent a sheet of flame directly across it.

“Now let the fire burn itself out—and it won’t take long at this rate!” cried Tom, as he and Mary stood in comparative safety, free from the menace of fire and out of that blinding, choking smoke.

Then, to Tom’s surprise, Mary burst out crying.

The young inventor, not much accustomed to tears, thought at first that Mary had been hurt in some way, perhaps burned by a flying brand.

“What is it? Tell me,” he urged, taking her in his arms as they stood in the cool darkness and safety of the cave.

“I’m—I’m all right!” gasped Mary, looking up at him as well as she could in the gloom.

“All right? Then, why are you crying?”

“Oh, it’s because—because I’m so glad we’re—we’re here—safe!” sobbed the girl.

“Oh!” exclaimed Tom, but there was a great deal of meaning in that one word. “Yes, I guess we’re all right,” he agreed.

He looked out of the cave. In front of it and on either side the fire was burning fiercely. Another few seconds and neither he nor Mary would have been able to get through that fierce, hot barrier. But the flames could not eat their way into the cavern.

Then, as he and the girl stood there, thankfulness in their hearts that they had thus come safely through two grave dangers, there suddenly sounded a deep, booming, vibrating sound that seemed to shake the earth about them.

“Dynamite!” cried Tom. “They’ve brought up explosives and are blowing up patches to stop the flames. A good idea!”

“No, that isn’t dynamite,” said Mary. “Don’t you know thunder when you hear it?”

“Thunder?” cried Tom Swift.

“Yes. It’s thundering! Don’t you remember, we saw signs of a storm coming up in the west just before the aeroplane went dead?”

“That’s right. If it is thunder——”

A booming crash interrupted him. There was no doubt of it, a heavy storm was pending.

“The rain will put out the forest fire,” concluded Tom. “Then we can get out of here and back home.”

“Home seems a long way off,” sighed Mary.

“We can make it pretty quickly by going down the brook,” suggested Tom. “The brook always rises a short time after even a little rain, for all the water in this section drains into it. I know where there’s a boat hidden in the bushes not far from here, and we can paddle down in that.”

“It sounds enticing,” returned Mary. “Oh, I look a fright, don’t I?” she asked, with a nervous giggle. Having been in the cave a little while, their eyes were more accustomed to the gloom and they could see better.

“You do not!” emphatically cried Tom, which, of course, was the right answer.

“It has been a wonderful experience,” she went on slowly. “Not that I would care to repeat it—Oh, Tom!”

She suddenly gave a gasp of fear and covered her eyes with her hands as a blinding flash of lightning seemed actually to shoot through the cavern. It was followed a second later by a crash of thunder which made even Tom Swift, used as he was to experimenting with big guns, jump.

“Here comes the rain!” he cried.

At that moment the storm broke with almost tropical fury, the big drops pelting down like hail on the burning trees, bushes and such dry leaves as had accumulated from the previous fall.

“This will douse the blaze,” went on the young inventor.

Certainly, no forest fire could continue in the face of such odds as a violent rain storm—and this storm was violent. Seldom had Tom seen it rain so hard. He and Mary stood in the entrance to the cave and watched the drops pelt down. They could observe the fire in front of them die away, the blaze flickering out and then the smoke ceasing.

“I guess those fire-fighters are glad of this!” observed Tom, as he remembered the hardworking men and boys.

“Indeed, yes,” agreed Mary.

For an hour or more the downpour continued, and every vestige of the forest fire was extinguished when at last the muttering of the thunder died away and the fierce glow of the lightning faded from the blackened clouds.

Tom stepped outside the cave and looked about him. In the distance he could hear the loud murmuring of the brook, now turned into a good-sized stream.

“Come on, Mary,” he called. “It’s all over. We might as well start. Your mother may be worried about you. I’ll find that boat and we’ll soon be in Shopton.”

“Oh, I do wish I had a comb or something!” exclaimed the girl as she emerged from the cavern, trying to pin her hair back to keep it out of her eyes.

“You look fine!” declared Tom, and he really meant it.

“I can’t help it, anyhow,” Mary said, smiling slightly. “Thanks, Tom.”

The boat was found where Tom knew it to be hidden—he had used it on some of his excursions with Ned—and soon he and his companion were riding in comparative comfort down the swift little stream. They passed through a region where the forest fire had eaten its devastating way, but now the danger was over, the rain having soaked and drenched the woods.

In due time Tom and his companion reached the outskirts of Shopton, and then, knowing Mary would like a little privacy, he went to the nearest telephone and called a taxicab from the town garage. It came out to get him and Mary, and a little later she was safe at home.

“Oh, Mary! I’ve been so worried about you!” cried Mrs. Nestor. “Where have you been?”

“Oh, aeroplaning, falling, climbing out of trees, forest-firing, thunder and lightning, boating and floating—those are just a few of our activities this afternoon,” replied Mary, with a little excited laugh.

“What does she mean, Tom?” asked the bewildered lady.

“Those are some of the things that happened to us,” the young inventor said. “It isn’t a bit exaggerated. I suppose you heard about the forest fire?”

“Yes; and we were much worried for those in its path. But Mr. Nestor said it wouldn’t come this way.”

“No, it was far enough off from you,” agreed Tom. “And it’s all over now. Well, I think I’ll get back. I took this afternoon off as a sort of rest and mental relaxation—and I got it!” he chuckled grimly.

“How is Mr. Newton’s case coming on, Tom?” asked Mrs. Nestor.

“We thought very well, but something curious turned up a few days ago,” answered the young inventor, but not going into details. “Mr. Plum and Mr. Newton are out of town now, running down some evidence.”

At that moment the telephone rang, and Mr. Nestor, answering it, exclaimed:

“Tom Swift? Yes, he’s here. Wait a minute and I’ll let you talk to him. It’s for you, Tom,” he said, as he handed him the receiver.

“Hello!” called Tom into the instrument. Then he recognized his father’s voice and was aware at once that something had happened. “What’s that?” he cried. “An attack on you and Mrs. Baggert? Are you hurt? I’ll be right over! Send Ned with the runabout! Yes, I’ll come right away!”

There was an anxious look on his face as he hung up the receiver and turned to his friends.

“What is it?” asked Mary. “Has anything happened?”

“Lots, apparently,” answered Tom, with a grim smile. “Just a little while ago, while my father was alone, working in our office, he was mysteriously attacked and momentarily knocked senseless. Mrs. Baggert, too, was knocked down; and when Eradicate came to help he was savagely set upon—not that it would take much to knock out the poor old fellow.”

“Who did it?” cried Mr. Nestor.

“Is your father much hurt?” asked Mary.

“Dad doesn’t know who did it,” Tom answered. “He isn’t much hurt, I’m glad to say, or he wouldn’t have been able to telephone. I didn’t get a chance to ask him how Mrs. Baggert and Rad were, but I don’t believe they’re in a serious condition or he would have told me. It’s the mysteriousness of the attack and what it may mean that alarms my father and, naturally, me also.”

“Do you want me to go back with you, Tom?” asked Mr. Nestor. “I may be able to help you.”

“Thank you, but I guess the worst is over. I’ll telephone back and let you know how matters stand as soon as I find out myself. Ned ought to be here in a little while if he has luck.”

“You mean if he isn’t smashed up hurrying here,” said Mary.

“Something like that—yes,” Tom answered.

Certainly, Ned got out of the electric runabout about all it was capable of, for soon after Mr. Swift had telephoned the news of the mysterious attack the honk of the machine was heard out front. Bidding his friends good-bye, the young inventor was rushed to the scene of the latest outrage on the part of his enemies.

That it was the work of some enemy, or enemies, Tom did not for an instant doubt. It was not the first time those jealous of his success had tried to wrest from him by unfair means the fruits of his talents and toils.

“What’s it all about, Ned?” he asked his manager, as he was rushed along in the electric car.

“Don’t know, Tom,” was the answer. “I had gone over to the bank, and I was delayed a little while. As a matter of fact, I stopped to hear some reports about the forest fire, for I was anxious about you.

“When I got back I found the office in confusion, and Eradicate, staggering about with a badly cut head, was telling some story about a big red-haired man who had burst in on your father and had tried to take some papers away from him. Mrs. Baggert, it seems, had come over to the office to bring your father a glass of milk which she thought he ought to have, and she tried to stop the attack. But the rascal went for her, too.

“As soon as I got in your father, having in the meanwhile located you at Mary’s house, sent me over to get you. That’s all I know about it.”

“Is dad all right?”

“Yes—nothing serious. Though he’s greatly upset, and that isn’t any too good for him. But he got only a slight blow on the head.”

“And a man with red hair did it,” mused Tom. “Red hair! I don’t know anybody with red hair who would be as desperate as all that. This is getting mysterious!”

The young inventor, followed by his manager and chum, hurried into the house.

Tom found Dr. Clayton putting the finishing touches to the dressing on a scalp wound Eradicate had sustained in the encounter. In one corner of the room Mrs. Baggert, a bandage around one hand, was endeavoring to get Mr. Swift to drink something from a cup.

“I tell you I’m all right,” insisted the old inventor. “I don’t need any catnip tea, my dear Mrs. Baggert!”

“But it will be good for your nerves. Won’t it, doctor?” asked the solicitous housekeeper.

“I guess it won’t do him any harm,” was the noncommittal answer. “There, Rad, now you’ll be all right,” he added. “You aren’t as badly hurt as you thought.”

“Say, this looks like a first-line dressing station!” exclaimed Tom, for a glance showed him that the situation was not as desperate as it had at first seemed. No one was seriously hurt.

“Three casualties, but they can all get back on the firing line soon,” announced Dr. Clayton, with a smile.

“Are you able to talk to me about it, Dad?” asked Tom.

“He should be in bed and taking hot catnip tea!” insisted Mrs. Baggert.

“You ought to be in bed yourself, Mrs. Baggert!” returned Mr. Swift in kindly tones. “That wound in your hand——”

“Pshaw! A mere scratch. I’ve done worse to myself lots of times with a darning needle!” she replied. “And I do wish you’d take this catnip tea!”

“I’m not a baby!” laughed Mr. Swift. “But, give it here!”

He had decided that this was the best way of getting rid of the insistent and troubled housekeeper. He drank the concoction, making rather a wry face over it, and then Mrs. Baggert, satisfied, went out of the room.

“Now let’s have the story,” suggested Tom. “Start at the beginning. Is Rad able to tell his part in it?” he inquired, as he placed a chair for the aged colored man.

“I shore is!” was the emphatic answer. “An’ ef dat red-haired rascal comes in yeah now I’ll lambaste him a good one—dat’s whut I will!”

“Better go easy, Rad,” advised the doctor, who was putting away the materials he had been using.

“It was this way, Tom—” said his father, and then, noticing the rather disheveled condition of his son, he exclaimed: “Were you attacked also?”

“No. I had a little trouble with the plane and had to sprint with a forest fire,” was the easy answer. “I’m all right. Go on.”

Thereupon Mr. Swift related that he had been at work in a room opening out of Tom’s main office on some figures Tom had asked him to verify when a man suddenly entered and without warning reached over the desk as if to grab the papers on which Mr. Swift was working.

“I gave a yell and leaped at him,” said the aged inventor, “but he struck me with something in his hand. I got dizzy and sank back in my chair. Just then Eradicate, who was out in the hall, rushed in and the man turned on him, giving poor Rad a blow that knocked him down.

“What happened after that I don’t know, except that I saw, in a daze, Mrs. Baggert enter the room and the man spring at her. Then I must have fainted. When I came to myself I was being looked after by Dr. Clayton. But I’m all right now. We must get after this rascal, Tom.”

“Certainly we will, Dad. But who was he? What does he look like? A red-haired man has been mentioned.”

“Yes, Tom, this fellow had closely-cropped red hair. I have never seen him before that I know of.”

“Had you, Rad?” asked the youth.

“No, Massa Tom. I was sweepin’ out in de hall an’ I had my back to de do’. I didn’t see de fellah go in. But I heard yo’ pa yell, den I bust in.”

“What happened then?” Tom wanted to know, while Ned made notes in shorthand of the answers, so he and Tom could go over it later.

“Well, de mostest whut happen is dat me an’ dat fellah come togetha,” explained Rad. “I went fo’ to hit him, but he done hit me fust! Golly, ef dey was ebber a time when I done wish fo’ dat giant, it was den!”

“Do all the descriptions of this man tally?” asked Tom. “I mean does Mrs. Baggert also say he was a stranger with red hair?”

“Yes,” answered Mr. Swift. “I questioned her about that before you got here. The fellow surely had red hair cut close to his head.”

“Did he get away with anything?” asked Tom quickly. “I mean any of our plans? What papers did you have out on the desk when he burst in on you. Dad?”

“They were the plans of both the tidal engine and the mill machinery that I was glancing over, you asked me to verify your figures, you know,” was the answer. “But he didn’t get any.”

The excitement was extreme while it lasted, but it was over now. Inquiries developed the fact that none of the employees in the office had seen the mysterious red-haired stranger enter or leave.

He had been evolved out of thin air, it seemed, and had vanished into the same element. That he had had his trouble for his pains was evident, for a careful check-up showed that none of the tidal engine papers was missing, nor had any of the mill machinery plans been taken from Mr. Swift.

“How about my chest of stuff?” asked Tom anxiously.

“It’s all right,” his father informed him. “I looked at that as soon as I felt able. It’s locked and still in place.”

“Good!” cried Tom. “And now we must get busy and solve this mystery.”

Making sure that his father, Rad and Mrs. Baggert were really in no danger, Tom took a bath to remove some of the grime of his recent experiences and then sent a couple of his men over to the pine tree in which the Hummer had lodged.

“I’m afraid the plane’s a goner,” Tom said. “But maybe you can save part of her. The engine ought to be good, anyhow.”

This having been done, and as it was now late in the day, Tom closed the office, first, however, arranging to have Koku take up his sleeping quarters there to be on guard every night.

“If the red-haired chap returns, he’ll meet with a different reception this time,” Tom said to Ned.

He and Ned made a careful check-up on all the incidents connected with the attempted robbery and assault. They looked about the place for clews, but found none of any moment. Nor could any one be found who had seen the scoundrel make his way to Mr. Swift’s room.

The young inventor had not forgotten what Mary had told him about the conversation in the restaurant, and he called up the proprietor on the telephone. But that individual could give him no information concerning the fellows who had had their meal there.

It was natural that Tom’s mind should jump to the latest acquisition to his working force—the man Barsky. Somewhat suspicious of him from the first, and these suspicions added to by his father’s ominous shake of the head and his expressed doubts of the Russian, Tom decided to keep an eye on the fellow.

It was almost closing time in the shops when Dr. Clayton had gone, leaving all his patients in good shape, and when Tom and Ned had been informed as to the main points in the matter. With his suspicions fermenting, Tom hurried over to the pattern shop.

It was with mingled feelings that he saw Barsky hard at work on certain important models. Tom passed the fellow and spoke to him, saying casually:

“It will soon be quitting time.”

“Eet matters not to me—hours,” replied the man in his strong accent. “When I work I think not of time. I am of much interest in my profession.”

“Yes, it’s a good thing to be so interested,” returned Tom dryly.

He passed on, but took a position where he could watch the man without himself being observed.

It was hot in the workshop. Beads of perspiration came out on Barsky’s forehead, and as he mopped them away with a big, blue handkerchief, Tom, from his hiding place, saw something that made him exclaim:

“The fellow’s wearing a wig!”

Wild ideas ran through Tom Swift’s mind.

“I’ll set a trap for him,” he decided.

The quitting whistle blew. True to his statement, the Russian worked on, though other men laid aside their tools. Tom remained in his hiding place, but it was now getting dark in the shop and he could see little.

It was not until shortly before noon the following day that Tom had a chance to put into operation his plan of laying a trap for Barsky. In the meanwhile nothing new had developed in the matter of discovering the red-haired man.

Carrying out his plan, Tom went to a small room in the rear of his office where he sometimes carried out delicate experiments. From there he caused to be sent to the suspect a message that he was wanted.

The approach to this little room was along a narrow corridor where there was not room for two to pass. When Tom heard Barsky approaching in answer to the summons, the young inventor hurried out, timing himself to meet the Russian in the corridor. To keep the matter secret, Tom had arranged to be alone in this part of the building.

“Ah, you sent for me, Mr. Swift?” asked the man. “Eet is a plaisair for to come to so distinguished an inventor.”

Thus the man exclaimed as he saw Tom coming toward him out of the little room. But Tom gave the fellow no chance to do anything, had such been his intention.

Brushing up against the suspect, as though to pass him in the narrow corridor, Tom raised his hand and brushed the big mop of black hair on Barsky’s head.

A moment later the wig of hair came off and with it the bushy black beard that all but hid the fellow’s face.

“Ah, I thought so!” cried Tom, as he saw closely-cropped red hair, heretofore hidden by the wig. “You’re a prison bird all right, Barsky—or whatever your name is. I’ve found you out!”

For a moment the man was so taken by surprise that he could only stand with open mouth, gasping.

Then, suddenly, rage seemed to take possession of the red-haired rascal—the same sort of rage that must have actuated him in his attack on Mr. Swift, Eradicate and Mrs. Baggert. Before he could speak, however, Tom cried:

“You’re through here, you dirty scoundrel! Get your time and clear out! And don’t think you’re going to have it end there. I’m going to have you arrested!”

“Oh, you are, eh?” sneered the man, and, realizing that his disguise had been effectually penetrated, all trace of his pretended Russian accent disappeared. He spoke ordinary English. “So you think you’ve found me out, do you? Well, you’ve got another guess coming, Tom Swift! I’m not half through with you!”

“You mean I’m not through with you!” replied Tom. “You’re an imposter! I have been suspecting you for some time, and my father has from the first. Now we’ll have a settlement!”

“But first I’ll settle with you!” cried the fellow, whose rage was on the increase. His lips closed tightly and he clenched his hands. These should have been warning signs to Tom, but they were not.

A moment later, kicking aside the wig and false beard, the fellow made a jump for the young inventor. Whether he held concealed in his hand some object like a black-jack, was never found out. But the fellow gave Tom such a blow on the head that the young inventor crumpled up and went down in a heap. Blackness closed over him and in his ears a multitude of bells seemed to ring.