Amazement held Mr. Boylan silent for a moment, and then, staring at Tom, as though he could not believe what he had heard the young inventor say, the representative of Mr. Peters exclaimed:

"Nothing doing?"

"That's what I said," repeated Tom, calmly.

"But--but you don't understand, I'm afraid."

"Oh, but indeed I do."

"Then you refuse to let my friend, Mr. Peters, exploit some of your inventions?"

"I refuse absolutely."

"Oh, come now. Take an invention that hasn't been very successful."

"Well, I don't like to boast," said Tom with a smile, "but all of my inventions have been successful. They don't need any aid from Mr. Peters, thank you."

"But this one!" went on the visitor eagerly, "this one about some new kind of telephone," and he motioned to the drawings on the table. "Has that been a success? Excuse me for having looked at the plans, but I did not think you would mind. Has that telephone been a success? If it has not perhaps Mr. Peters could form a company to--"

"How did you know those drawings referred to a telephone?" asked Tom, suspiciously, for the papers did not make it clear just what the invention was.

"Why, I understood--I heard, in fact, that you were working on a new photo telephone, and--"

"Who told you?" asked Tom quickly.

"Oh, no one in particular. The colored man who sent me here mentioned--"

"Eradicate!" thought Tom. "He must have been talking. That isn't like him. I must look into this."

Then to his caller he said:

"Really, you must excuse me, Mr. Boylan, but I don't care to do any business with Mr. Peters. Tell him, with my thanks, that there is really nothing doing in his line. I prefer to exploit my own inventions."

"That is your last word?"

"Yes," returned Tom, as he gathered up the drawings.

"Well," said Mr. Boylan, and Tom could not help thinking there was a veiled threat in his tones, "you will regret this. You will be sorry for not having accepted this offer."

"I think not," replied Tom, confidently. "Good-day."

The young inventor sat for some time thinking deeply, when his visitor had gone. He called Eradicate to him, and gently questioned the old colored man, for Eradicate was ageing fast of late, and Tom did not want him to feel badly.

It developed that the servant had been closely cross-questioned by Mr. Boylan, while he was waiting for Tom, and it was small wonder that the old colored man had let slip a reference to the photo telephone. But he really knew nothing of the details of the invention, so he could have given out no secrets.

"But at the same time," mused Tom, "I must be on guard against these fellows. That Boylan seems a pretty slick sort of a chap. As for Peters, he's a big 'bluff,' to be perfectly frank. I'm glad I had Mr. Damon's warning in mind, or I might have been tempted to do business with him."

"Now to get busy at this photo telephone again. I'm going to try a totally different system of transmission. I'll use an alternating current on the third wire, and see if that makes it any better. And I'll put in the most sensitive selenium plate I can make. I'm going to have this thing a success."

Tom carefully examined the drawings of his invention, at which papers Mr. Boylan had confessed to looking. As far as the young inventor could tell none was missing, and as they were not completed it would be hard work for anyone not familiar with them to have gotten any of Tom's ideas.

"But at the same time I'm going to be on my guard," mused Tom. "And now for another trial."

Tom Swift worked hard during the following week, and so closely did he stick to his home and workshop that he did not even pay a visit to Mr. Damon, so he did not learn in what condition that gentleman's affairs were. Tom even denied himself to his chum Ned, so taken up was the young inventor with working out the telephone problem, until Ned fairly forced himself into the shop one day, and insisted on Tom coming out.

"You need some fresh air!" exclaimed Ned. "Come on out in the motor boat again. She's all fixed now; isn't she?"

"Yes," answered Tom, "but--"

"Oh, 'but me no buts,' as Mr. Shakespeare would say. Come on, Tom. It will do you good. I want a spin myself."

"All right, I will go for a little while," agreed Tom. "I am feeling a bit rusty, and my head seems filled with cobwebs."

"Can't get the old thing to come out properly; eh?"

"No. I guess dad was more than half right when he said it couldn't be done. But I haven't given up. Maybe I'll think of some new plan if I take a little run. Come along."

They went down to the boat house, and soon were out on the lake in the Kilo.

"She runs better since you had her fixed," remarked Ned.

"Yes, they did a good job."

"Did you sue Peters?"

"Didn't have to. He sent the money," and Tom told of his interview with Mr. Boylan. This was news to Ned, as was also the financial trouble of Mr. Damon.

"Well," said the young banker, "that bears out what I had heard of Peters--that he was a get-rich-quick chap, and a good one to steer clear of."

"Speaking of steering clear," laughed Tom, "there he is now, in his big boat," and he pointed to a red blur coming up the lake. "I'll give him a wide enough berth this time."

But though Mr. Peters, in his powerful motor boat, passed close to Tom's more modest craft, the big man did not glance toward our hero and his chum. Nor did Mr. Boylan, who was with his friend, look over.

"I guess they've had enough of you," chuckled Ned.

"Probably he wishes he hadn't paid me that money," said Tom. "Very likely he thought, after he handed it over, that I'd be only too willing to let him manage one of my inventions. But he has another guess coming."

Tom and Ned rode on for some distance, thoroughly enjoying the spin on the lake that fine Summer day. They stopped for lunch at a picnic resort, and coming back in the cool of the evening they found themselves in the midst of a little flotilla of pleasure craft, all decorated with Japanese lanterns.

"Better slow down a bit," Ned advised Tom, for many of the pleasure craft were canoes and light row boats. "Our wash may upset some of them."

"Guess you're right, old man," agreed Tom, as he closed the gasolene throttle, to reduce speed. Hardly had he done so than there broke in upon the merry shouts and singing of the pleasureseekers the staccato exhaust of a powerful motor boat, coming directly behind Tom's craft.

Then came the shrill warning of an electrical siren horn.

"Somebody's in a hurry," observed Tom.

"Yes," answered Ned. "It sounds like Peters's boat, too."

"It is!" exclaimed Tom. "Here he comes. He ought to know better than to cut through this raft of boats at that speed."

"Is he headed toward us?"

"No, I guess he's had enough of that. But look at him!"

With undiminished speed the burly promoter was driving his boat on. The big vibrating horn kept up its clamor, and a powerful searchlight in front dazzled the eyes.

"Look out! Look out!" cried several.

Many of the rowers and paddlers made haste to clear a lane for the big, speedy motor craft, and Peters and his friends (for there were several men in his boat now) seemed to accept this as a matter of course, and their right.

"Somebody'll be swamped!" exclaimed Ned.

Hardly had he spoken than, as the big red boat dashed past in a smother of foam, there came a startled cry in girls' voices.

"Look!" cried Tom. "That canoe's upset! Speed her up, Ned! We've got to get 'em!"

"Where are they?"

"Who are they?"

"Over this way! There's their canoe!"

"Look out for that motor boat!"

"Who was it ran them down? They ought to be arrested!"

These were only a few of the cries that followed the upsetting of the frail canoe by the wash from the powerful red boat. On Tom's Kilo there was a small, electrical searchlight which he had not yet switched on. But, with his call to Ned Newton to speed up the motor, that had been slowed down, Tom, with one turn of his fingers, set the lamp aglow, while, with the other hand, he whirled the wheel over to head his craft for the spot where he saw two figures struggling in the water.

Fortunately the lanterns on the various canoes and row-boats, as well as the light on the bow of Tom's Kilo, made an illumination that gave the rescuers a good chance to work. Many other boats besides Tom's had headed for the scene, but his was the more practical, since the others--all quite small ones--were pretty well filled.

"There they are, Ned!" Tom suddenly cried. "Throw out the clutch! I'll get 'em!"

"Want any help?"

"No, you stay at the engine, and mind what I say. Reverse now! We're going to pass them!"

Ned threw in the backing gear, and the screw churned the water to foam under the stern of the Kilo.

Tom leaned over the bow, and made a grab for the gasping, struggling figure of a girl in the water. At the same time he had tossed overboard a cork life ring, attached to a rope which, in turn, was made fast to the forward deck-cleat. "Grab that!" cried Tom. "Hold on, and I'll have you out in a second! That's enough, Ned! Shut her off!"

The Kilo came to a standstill, and, a second later, Tom had pulled into his boat one of the girls. She would have collapsed, and fallen in a heap on the bottom boards, had not Ned, who had come forward from the engine, caught her.

Then Tom, again leaning over the side, pulled in the other girl, who was clinging to the life ring.

"You're all right," Tom assured her, as she came up, gasping, choking and crying hysterically. "You're all right!"

"Is--is Minnie saved?" she sobbed.

"Yes, Grace! I'm here," answered the one Ned was supporting.

"Oh, wasn't it terrible!" cried the second girl Tom had saved.

"I thought we would be drowned, even though we can swim."

"Yes, it--it was so--so sudden!" gasped her companion. "What happened?"

"The wash from that big boat upset you," explained Tom. "That fellow ought to be ashamed of himself, rushing along the way he did. Now, can I take you girls anywhere? Your canoe seems to have drifted off."

"I have it!" someone called. "It's turned over, but I can tow it to shore."

"And I'll take the girls home," offered a gentleman in a large rowboat. "My wife will look after them. They live near us," and he mentioned his own name and the names of the two girls Tom had saved. The young inventor did not know them, but he introduced himself and Ned.

"This is the annual moonlight outing of our little boat club," explained the man who had offered to look after the girls, "and it is the first time we ever had an accident. This was not our fault, though."

"Indeed it was not," agreed Tom, after he had helped the two dripping young ladies into the rowboat. "It was due to Mr. Peters's speed mania."

"I shall make a complaint against him to the navigation authorities," said Mr. Ralston, who was looking after the girls. "He must think he, alone, has any rights on this lake."

With renewed thanks to Tom and Ned, the rescued girls were rowed off to their homes, while the interrupted water carnival was continued.

"Some little excitement; eh, Tom?" remarked Ned, when they were once more under way.

"Yes. We seem to run into that fellow Peters, or some of his doings, quite often lately."

"And it isn't a good sign, either," murmured Ned.

For some minutes after that Tom did not speak. In fact he was so silent that Ned at last inquired:

"What's the matter, Tom--in love?"

"Far from it. But, Ned, I've got an idea."

"And I've got a wet suit of clothes where that nice young lady fainted in my arms. I'm soaked."

"That's what gave me the idea--the water, I mean. I noticed how everything was reflected in it, and, do you know, Ned, I believe I have been working on the wrong principle for my photo telephone."

"Wrong, Tom, how is that?"

"Why, I've been using a dry plate, and I think I should have used a wet one. You know how even in a little puddle of water on the sidewalk you can see yourself reflected?"

"Yes, I've often seen that."

"Well then, 'bless my watch chain!' as Mr. Damon would say, I think I've got just what I want. I'm going to try a wet plate now, and I think it will work. Come on now. Speed up! I'm in a great big hurry to get home and try it!"

"Well, Tom, I sure will be glad if you've got the right idea," laughed Ned. "It will be worth getting wet through for, if you strike something. Good luck!"

Tom could hardly wait to fasten up his boat for the night, so eager was he to get to his shop laboratory and try the new idea. A gleam of hope had come to him.

It was still early evening, and Tom, when enticed out by Ned, had left his photo telephone apparatus in readiness to go on with his trials as soon as he should have come back.

"Now for it, Ned!" exclaimed the young inventor, as he took off his coat. "First I'll sensitize a selenium plate, and then I'll wet it. Water is always a good conductor of electricity, and it's a wonder that I forgot that when I was planning this photo telephone. But seeing the sparkle of lights, and the reflection of ourselves in the lake to-night, brought it back to me. Now then, you haven't anything special to do; have you?"

"Not a thing, Tom."

"That's good. Then you get in this other telephone closet--the one in the casting shop. I'll put a prepared plate in there, and one in the booth where I'm to sit. Then I'll switch on the current, and we'll see if I can make you out, and you notice whether my image appears on your plate."

It took some little time to make ready for this new test. Tom was filled with enthusiasm, and he was sure it was going to be successful this time. Ned watched him prepare the selenium plates--plates that were so sensitive to illumination that, in the dark, the metal would hardly transmit a current of electricity, but in the light would do so readily, its conductivity depending on the amount of light it received.

"There, I guess we're all ready, Ned," announced Tom, at last. "Now you go to your little coop, and I'll shut myself up in mine. We can talk over the telephone."

Seated in the little booth in one of the smaller of Tom's shops, Ned proceeded with his part in the new experiment. A small shelf had been fitted up in the booth, or closet, and on this was the apparatus, consisting of a portable telephone set, and a small box, in which was set a selenium plate. This plate had been wet by a spray of water in order to test Tom's new theory.

In a similar booth, several hundred feet away, and in another building, Tom took his place. The two booths were connected by wires, and in each one was an electric light.

"All ready, Ned?" asked Tom, through the telephone.

"All ready," came the answer.

"Now then, turn on your switch--the one I showed you--and look right at the sensitized plate. Then turn out your light, and slowly turn it on. It's a new kind, and the light comes up gradually, like gas or an oil lamp. Turn it on easily."

"I get you, Tom."

Ned did as requested. Slowly the illumination in the booth increased.

"Do you get anything, Tom?" asked Ned, over the wire.

"Not yet," was the somewhat discouraged answer. "Go ahead, turn on more light, and keep your face close to the plate."

Ned did so.

"How about it now?" he asked, a moment later.

"Nothing--yet," was the answer. And then suddenly Tom's voice rose to a scream over the wire.

"Ned--Ned! Quick!" he called. "Come here--I--I--"

The voice died off into a meaningless gurgle.

Ned Newton never knew exactly how he got out of the telephone booth. He seemed to give but one jump, tearing the clamped receiver from his ear, and almost upsetting the photo apparatus in his mad rush to help Tom. Certain it is, however, that he did get out, and a few seconds later he was speeding toward the shop where Tom had taken his position in a booth.

Ned burst in, crying out:

"Tom! What is it? What happened? What's the matter?"

There was no answer. Fearing the worst, Ned hurried to the small booth, in one corner of the big, dimly lighted shop. He could see Tom's lamp burning in the telephone compartment.

"Tom! Tom!" called the young banker.

Still there was no answer, and Ned, springing forward, threw open the double, sound-proof door of the booth. Then he saw Tom lying unconscious, with his head and arms on the table in front of him, while the low buzzing of the electrical apparatus in the transmitting box told that the current had not been shut off.

"Tom! Tom!" cried Ned in his chum's ear. He shook him by the shoulder.

"Are you hurt? What is the matter?"

The young inventor seemed unconscious, and for a moment Ned had a wild idea that Tom had been shocked to death, possibly by some crossed live wire coming in contact with the telephone circuit.

"But that couldn't have happened, or I'd have been shocked myself," mused Ned.

Then he became aware of a curious, sweet, sickish odor in the booth. It was overpowering. Ned felt himself growing dizzy.

"I have it--chloroform!" he gasped. "In some way Tom has been overcome by chloroform. I've got to get him to the fresh air."

Once he had solved the puzzle of Tom's unconsciousness, Ned was quick to act. He caught Tom under the arms, and dragged him out of the booth, and to the outer door of the shop. Almost before Ned had reached there with his limp burden, Tom began to revive, and soon the fresh, cool night air completed the work.

"I--I," began the young inventor. "Ned, I--I--"

"Now take it easy, Tom," advised his chum. "You'll be all right in a few minutes. What happened? Shall I call your father, or Koku?"

"No--don't. It would only--only alarm dad," faltered Tom. "I'm getting all right now. But he--he nearly had me, Ned!"

"He had you? What do you mean, Tom? Who had you?"

"I don't know who it was, but when I was talking to you over the wire, all of a sudden I felt a hand behind me. It slipped over my mouth and nose, and I smelled chloroform. I knew right away something was wrong, and I called to you. That's all I remember. I guess I must have gone off."

"You did," spoke Ned. "You were unconscious when I got to you. I couldn't imagine what had happened. First I thought it was an electrical shock. Then I smelled that chloroform. But who could it have been, Tom?"

"Give it up, Ned! I haven't the slightest idea."

"Could they have been going to rob you?"

"I haven't a thing but a nickel watch on me," went on Tom. "I left all my cash in the house. If it was robbery, it wasn't me, personally, they were after."

"What then? Some of your inventions?"

"That's my idea now, Ned. You remember some years ago Jake Burke and his gang held me up and took one of dad's patents away from me?"

"Yes, I've heard you mention that. It was when you first got your motor cycle; wasn't it?"

"That's right. Well, what I was going to say was that they used chloroform on me then, and--"

"You think this is the same crowd? Why, I thought they were captured."

"No, they got away, but I haven't heard anything of them in years. Now it may be they have come back for revenge, for you know we got back the stolen property."

"That's right. Say, Tom, it might be so. What are you going to do about it?"

"I hardly know. If it was Jake Burke, alias Happy Harry, and his crowd, including Appleson, Morse and Featherton, they're a bad lot. I wouldn't want father to know they were around, for he'd be sure to worry himself sick. He never really got over the time they attacked me, and got the patent away. Dad sure thought he was ruined then."

"Now if I tell him I was chloroformed again to-night, and that I think it was Burke and his crowd, he'd be sure to get ill over it. So I'm just going to keep mum."

"Well, perhaps it's the best plan. But you ought to do something."

"Oh, I will, Ned, don't worry about that. I feel much better now."

"How did it happen?" asked Ned, his curiosity not yet satisfied.

"I don't know, exactly. I was in the booth, talking to you, and not paying much attention to anything else. I was adjusting and readjusting the current, trying to get that image to appear on the plate. All at once, I felt someone back of me, and, before I could turn, that hand, with the chloroform sponge, was over my mouth and nose. I struggled, and called out, but it wasn't much use."

"But they didn't do anything else--they didn't take anything; did they, Tom?"

"I don't know, Ned. We'll have to look around. They must have sneaked into the shop. I left the door open, you see. It would have been easy enough."

"How many were there?"

"I couldn't tell. I only felt one fellow at me; but he may have had others with him."

"What particular invention were they after, Tom?"

"I'm sure I don't know. There are several models in here that would be valuable. I know one thing, though, they couldn't have been after my photo telephone," and Tom laughed grimly.

"Why not?" Ned wanted to know.

"Because it's a failure--that's what! It's a dead, sure failure, Ned, and I'm going to give it up!" and Tom spoke bitterly.

"Oh, don't say that!" urged his chum. "You may be right on the verge of perfecting it, Tom. Didn't you see any image at all on the plate?"

"Not a shadow. I must be on the wrong track. Well, never mind about that now. I'm going to look around, and see if those fellows took anything."

Tom was feeling more like himself again, the effects of the chloroform having passed away. He had breathed the fumes of it for only a little while, so no harm had been done. He and Ned made an examination of the shop, but found nothing missing.

There were no traces of the intruders, however, though the two chums looked carefully about outside the building.

"You were too quick for them, Ned," said Tom. "You came as soon as I called. They heard me speaking, and must have known that I had given the alarm."

"Yes, I didn't lose any time," admitted Ned, "but I didn't see a sign of anyone as I ran up."

"They must have been pretty quick at getting away. Well, now to decide what's best to do to-night."

After some consultation and consideration it was decided to set the burglar alarms in every building of the Swift plant. Some time previous, when he had been working on a number of valuable inventions, unscrupulous men had tried to steal his ideas and models. To prevent this Tom had arranged a system of burglar alarms, and had also fitted up a wizard camera that would take moving pictures of anyone coming within its focus. The camera could be set to work at night, in connection with the burglar alarms.

The apparatus was effective, and thus an end was put to the efforts of the criminals. But now it seemed Tom would have to take new precautionary measures. His camera, however, was not available, as he had loaned it to a scientific society for exhibition.

"But we'll attach the burglar wires," decided Tom, "and see what happens."

"It might be a good plan to have Koku on guard," said Tom's chum. "That giant could handle four or five of the chaps as easily as you and I could tackle one."

"That's right," agreed Tom. "I'll put him on guard. Whew! That chloroform is giving me a headache. Guess I'll go to bed. I wish you'd stay over to-night, Ned, if you haven't anything else to do. I may need you."

"Then of course I'll stay, Tom. I'll telephone home that I won't be in."

A little later Tom had put away his new photo telephone apparatus, and had prepared for the warm reception of any unbidden callers.

"I wish I hadn't started on this new invention," said Tom, half bitterly, as he locked up the main parts of his machine, "I know it will never work."

"Oh, yes it will," spoke Ned, cheerfully. "You never failed yet, Tom Swift, in anything you undertook, and you're not going to now."

"Well, that's good of you to say, Ned, but I think you're wrong this time. But I'm not going to think any more about it to-night, anyhow. Now to find Koku and put him on watch."

The giant listened carefully to Tom's simple instructions.

"If any bad men come in the night, Koku," said the young inventor, "you catch them!"

"Yes, master, me catch!" said Koku, grimly. "Me catch!" and he stretched out his powerful arms, and clenched his big hands in a way that boded no good to evildoers.

Nothing was said to Mr. Swift, to Mrs. Baggert, or to Eradicate about what had happened, for Tom did not want to worry them. The burglar alarms were set, Koku took his place where he could watch the signals, and at the same time be ready to rush out, for, somehow, Tom had an idea that the men who had attacked him would come back.

Tom and Ned occupied adjoining rooms, and soon were ready for bed. But, somehow, Tom could not sleep. He lay awake, tossing from side to side, and, in spite of his resolution not to think about his photo telephone invention, his mind ran on nothing but that.

"I can't see what next to do to make it work," he told himself, over and over again. "Something is wrong--but what?"

At length he fell into a fitful doze, and he had a wild dream that he was sliding down hill on a big mirror in which all sorts of reflections were seen--reflections that he could not get to show in the selenium plates.

Then Tom felt the mirror bobbing up and down like a motor boat in a storm. He felt the vibration, and he heard a voice calling in his ear:

"Get up, Tom! Get up!"

"Yes! What is it?" he sleepily exclaimed,

"Hush!" was the caution he heard, and then he realized that his dream had been caused by Ned shaking him.

"Well?" whispered Tom, in tense tones.

"Midnight visitors!" answered his chum "The burglar alarm has just gone off! The airship hangar drop fell. Koku has gone out. Come on!"

Tom leaped silently out of bed, and stood for a moment half dazed, so soundly had he been sleeping.

"Come on!" urged Ned softly, realizing that his chum had not fully comprehended. "Koku will hold them until we get there. I haven't roused anyone else."

"That's right," whispered Tom, as he began putting on his clothes. "I don't want father to know. When did it happen?"

"Just a little while ago. I couldn't sleep very well, but I fell into a doze, and then I heard the buzzer of the alarm go off. I saw that the drop, showing that the hangar had been entered, had fallen. I got to the window in time to see Koku going toward the shed from his little coop. Then I came to you."

"Glad you did," answered Tom. "I didn't think I was sleeping so soundly."

Together the two chums made their way from their rooms down the dimly-lighted hall to a side door, whence they could reach the airship hangar, or shed.

"Won't we need something--a gun or--" began Ned.

"Clubs are better--especially at night when you can't see to aim very well," whispered back Tom. "I've got a couple of good ones downstairs. I could use my electric rifle, and set it merely to disable temporarily whoever the charge hit, but it's a little too risky. Koku has a habit of getting in the way at the most unexpected times. He's so big, you know. I think clubs will be best."

"All right, Tom, just as you say," agreed Ned. "But who do you think it can be?"

"I haven't the least idea. Probably the same fellows who were after me before, though. This time I'll find out what their game is, and what they're after."

The chums reached the lower hall, and there Tom picked out two African war clubs which he had brought back with him from one of his many trips into wild lands.

"These are just the thing!" exclaimed Ned, swinging his about.

"Careful," cautioned Tom, "If you hit something you'll rouse the house, and I don't want my father and Mrs. Baggert, to say nothing of Eradicate, awakened."

"Excuse me," murmured Ned. "But we'd better be getting a move on."

"That's right," agreed Tom. He dropped into a side pocket a small but powerful electric flash lamp, and then he and Ned let themselves out.

There had been a bright moon, but it was now overcast by clouds. However, there was sufficient light to enable the two lads to see objects quite clearly. All about them were the various buildings that made up the manufacturing and experimental plant of Tom Swift and his father. Farthest away from the house was the big shed where once Tom had kept a balloon, but which was now given over to his several airships. In front of it was a big, level grassy space, needed to enable the aircraft to get a "running start" before they could mount into the clouds.

"See anything of Koku?" whispered Ned.

"No," answered Tom, in the same cautious voice. "I guess he must be hiding--"

"There he goes now!" hissed Ned, pointing to a big figure that was approaching the hangar. It was undoubtedly that of the giant, and he could be seen, in the dim light, stalking cautiously along.

"I wonder where the uninvited guests are?" asked Tom.

"Probably in the airship shed," answered Ned. "Koku was after them as soon as the alarm went off, and they couldn't have gotten away. They must be inside there yet. But what can their game be?"

"It's hard to say," admitted Tom. "They may be trying to get something belonging to me, or they may imagine they can pick up some valuable secrets. Or they may--" He stopped suddenly, and then exclaimed:

"Come on, Ned! They're after one of the airships! That's it! My big biplane is all ready to start, and they can get it in motion inside of a few seconds. Oh, why didn't I hurry?" he added, bitterly.

But the hangar was still some distance away, and it would take two or three minutes of running to reach it.

Meanwhile, and at the instant Tom had his thought of the possible theft of his biggest aircraft, something happened.

The doors of the shed were suddenly thrown open, and the two boys could see the large airship being wheeled out. The hazy light of the moon behind the clouds shone on the expanse of white planes, and on the fish-tail rudder, one of Tom's latest ideas.

"Hey, there!" cried Tom, warningly.

"Leave that alone!" yelled Ned.

"Koku! Koku!" shouted Tom, shrilly. "Get after those fellows!"

"Me get!" boomed out the giant, in his deep voice.

He had been standing near the entrance to the hangar, probably waiting for developments, and watching for the arrival of Tom and Ned. The big form was seen to leap forward, and then several dark shadows swarmed from around the airship, and were seen to fling themselves upon the giant.

"That's a fight!" cried Ned. "They're attacking him!"

"Koku can take care of himself!" murmured Tom. "But come on. I don't see what their game is."

He understood a moment later, however, for while several of the midnight visitors were engaged in a hand-to-hand tussle with the giant there came a sharp, throbbing roar of the airship motor in motion. The propellers were being whirled rapidly about.

"Koku! Koku!" cried Tom, for he was still some distance off. "Never mind them! Don't let the airship be taken!"

But Koku could only grunt. Big and strong as he was, half a dozen men attacking him at once hampered him. He threw them from him, one after another, and was gradually making his way toward the now slowly-moving airship. But would he be in time?

Tom and Ned could not hope to reach the machine before Koku, though they were running at top speed.

"Koku! Koku!" yelled Tom. "Don't let them get away!"

But Koku could only grunt--harder this time--for he fell heavily, being tripped by a stick thrust between his legs. He lay for a moment stunned.

"They're going to get away!" panted Tom, making an effort to increase his speed.

"That's what!" agreed Ned.

Even as they spoke the roar of the airship motor increased. Several of the dark forms which had been engaged in the struggle with Koku were seen to pick themselves up, and run toward the airship, that was now in motion, moving on the bicycle wheels over the grass plot, preparatory to mounting upward in the sky.

"Stop! Stop!" commanded Tom. But it was all in vain.

The men leaped aboard the airship, which could carry six persons, and a moment later, with a deafening roar, as the engine opened up full, the big craft shot upward, taking away all but two of the midnight visitors. These, who had seemingly been stunned by Koku, now arose from the ground, and staggered off in the darkness.

"Get them!" cried Tom.

"We must see to Koku!" added Ned, "Look, there goes your airship, Tom!"

"Yes, I know. But we can't stop that now. Let's see if we can get a clew in these fellows!"

He pointed toward the two who had run off in the dark underbrush surrounding the hangar plaza, and he and Ned trailed them as well as they could. But from the first they knew it would be useless, for there were many hiding places, and, a little way beyond, was a clump of trees.

After a short search Tom gave up reluctantly, and came back to where Koku was now sitting on the ground.

"Are you hurt?" he asked of the giant.

"My mind hurt--that all," said the big man.

"I guess he means his feelings are hurt," Tom explained. "Do you know who they were, Koku?"

"No, master."

"But we must do something!" cried Ned. "They've got your airship, Tom."

"I know it," said the young inventor, calmly. "But we can't do anything now. You can hardly hear her, let alone see her. She's moving fast!"

He pointed upward to the darkness. Like some black bird of prey the airship was already lost to sight, though it would have seemed as if her white planes might render her visible. But she had moved so swiftly that, during the short search, she had already disappeared.

"Aren't you going to do anything?" asked Ned.

"Certainly," spoke Tom. "I'm going to telephone an alarm to all the nearby towns. This is certainly a queer game, Ned."

Disappointed and puzzled, Tom and Ned went to where Koku was standing in rather a dazed attitude. The giant, like all large bodies, moved slowly, not only bodily but mentally. He could understand exactly what had happened, except that he had not prevailed over the "pygmies" who had attacked him. They had been too many for him.

"Let's take a look inside," suggested Tom, when, by another glance upward, he had made sure that all trace of his big airship was gone. "Maybe we can get a clew. Then, Koku, you tell us what happened."

"It all happened to me," said the giant, simply. "Me no make anything happen to them."

"That's about right," laughed Tom, ruefully. "It all happened to us."

The lights in the hangar were switched on, but a careful search revealed little. The men, half a dozen or more, had come evidently well prepared for the taking away of Tom Swift's airship, and they had done so.

Entrance had been effected by forcing a small side door. True, the burglar alarm had given notice of the presence of the men, but Tom and Ned had not acted quite quickly enough. Koku had been at the hangar almost as soon as the men themselves, but he had watched and waited for orders, instead of going in at once, and this had given the intruders time to wheel out the craft and start the motor.

"Why didn't you jump right in on them when you saw what they were up to, Koku?" asked Tom.

"Me wait for master. Me think master want to see who men were. Me go in--they run."

"Well, of course that's so, in a way," admitted Tom. "They probably would have run, but they'd have run without my airship instead of with it, if they hadn't had time to get it outside the hangar. However, there's no use in crying over lost biplanes. The next thing is how to get her back. Did you know any of the men, Koku?"

"No, master."

"Then we haven't any clew that way. They laid their plans well. They just let you tangle yourself up with them, Koku, while the head ones got the motor going; an easy matter, since it was all ready to start. Then they tripped you, Koku, and as many of them as could, made a jump for the machine. Then they were off."

"Well, what's the next thing to do?" asked Ned, when another look about the shed had shown that not the slightest clew was available.

"I'm going to do some telephoning," Tom stated. "A big airship like mine can't go scooting around the country without being noticed. And those fellows can't go on forever. They've got to have gasolene and oil, and to get them they'll have to come down. I'll get it back, sooner or later; but the question is: Why did they take her?"

"To sell," suggested Ned.

"I think not," Tom said. "A big airship like mine isn't easy to sell. People who would buy it would ask questions that might not easily be answered. I'm inclined to think that some other reason made them take her, and it's up to us to find out what it was. Let's go into the house."

"Hark!" suddenly exclaimed Ned, holding up his hand for silence. They all heard footsteps outside the hangar.

Tom sprang to the door, flashing his electric light, and a voice exclaimed:

"Golly! Chicken thieves!"

"Oh, is it you, Eradicate?" asked the young inventor, with a laugh. "No, it isn't chicken thieves--they were after bigger game this time."

"Suffin happen?" asked the colored man. "Massa Swift he heah a noise, an' see a light, an' he sent me out yeah t' see what all am gwine on."

"Yes, something happened," admitted Tom. "They got the Eagle, Rad."

"What! Yo' big airship?"

"Yes."

"Huh! Dat's too bad, Massa Tom. I suah am sorry t' heah dat. Who done it?"

"We don't know, Rad."

"Maybe it was dat low-down cousin ob mine what tried t' git mah chickens, onct!"

"No, Rad, it wasn't your cousin. But I'll telephone the alarm to the police. They may be able to help me get the Eagle back."

Within the next hour several messages were sent to the authorities of nearby towns, asking them to be on the watch for the stolen airship. This was about all that could be done, and after Mr. Swift had been told the story of the night's happenings, everyone went back to bed again.

Further search the next morning brought forth no clews, though Tom, Ned and the others beat about in the bushes where the men had disappeared.

One or two reports were heard from surrounding towns, to the effect that several persons had heard a strange throbbing sound in the night, that, possibly, was caused by the passage of the airship overhead. One such report came from Waterford, the home town of Mr. Damon.

"Let's go over there," suggested Ned, to his chum. "I'd like to see our friend, and maybe we can get some other clews by circulating around there."

"Oh, I don't know," spoke Tom, rather listlessly.

"Why not?" Ned wanted to know.

"Well, I ought to be working on my photo telephone," was the answer. "I've got a new idea now. I'm going to try a different kind of current, and use a more sensitive plate. And I'll use a tungsten filament lamp in the sending booth."

"Oh, let your experiments go for a little while, Tom," suggested Ned. "Come on over to Mr. Damon's. The trouble with you is that you keep too long at a thing, once you start."

"That's the only way to succeed," remarked Tom. "Really, Ned, while I feel sorry about the airship, of course, I ought to be working on my telephone. I'll get the Eagle back sooner or later."

"That's not the way to talk, Tom. Let's follow up this clew."

"Well, if you insist on it I suppose I may as well go. We'll take the little monoplane. I've fixed her up to carry double. I guess--"

Tom Swift broke off suddenly, as the telephone at his elbow rang.

"Hello," he said, taking off the receiver. "Yes, this is Tom Swift. Oh, good morning, Mrs. Damon! Eh! What's that? Mr. Damon has disappeared? You don't tell me! Disappeared! Yes, yes, I can come right over. Be there in a few minutes. Eh? You don't know what to make of it? Oh, well, maybe it can easily be explained. Yes, Ned Newton and I will be right over. Don't worry."

Tom hung up the receiver and turned to his chum.

"What do you think of that?" he asked.

"What is it?"

"Why, Mr. Damon mysteriously vanished last night, and this morning word came from his bankers that every cent of his fortune had disappeared! He's lost everything!"

"Maybe--maybe--" hesitated Ned.

"No, Mr. Damon isn't that kind of a man," said Tom, stoutly. "He hasn't made away with himself."

"But something is wrong!"

"Evidently, and it's up to us to find out what it is. I shouldn't be surprised but that he knew of this coming trouble and started out to prevent it if he could."

"But he wouldn't disappear and make his wife worry."

"No, that's so. Well, we'll have to go over there and find out all about it."

"Say, Tom!" exclaimed Ned, as they were getting the small, but swift monoplane ready for the flight, "could there be any connection with the disappearance of Mr. Damon and the taking of the Eagle?"

Tom started in surprise.

"How could there be?" he asked.

"Oh, I don't know," answered Ned. "It was only an idea."

"Well, we'll see what Mrs. Damon has to say," spoke the young inventor, as he took his seat beside Ned, and motioned to Koku to twirl the propeller.

"Oh, Tom Swift! I'm so glad to see you!"

Mrs. Damon clasped her arms, in motherly fashion, about the young inventor. He held her close, and his own eyes were not free from tears as he witnessed the grief of his best friend's wife.

"Now, don't worry, Mrs. Damon," said Tom, sympathetically. "Everything will be all right," and he led her to a chair.

"All right, Tom! How can it be?" and the lady raised a tear-stained face. "My husband has disappeared, without a word! It's just as if the earth had opened and swallowed him up! I can't find a trace of him! How can it be all right?"

"Well, we'll find him, Mrs. Damon. Don't worry. Ned and I will get right to work, and I'll have all the police and detectives within fifty miles on the search--if we have to go that far."

"Oh, it's awfully good of you, Tom. I--I didn't know who else to turn to in my trouble but you."

"And why shouldn't you come to me? I'd do anything for you and Mr. Damon. Now tell me all about it."

Tom and Ned had just arrived at the Damon home in the airship, to find the wife of the eccentric man almost distracted over her husband's strange disappearance.

"It happened last night," Mrs. Damon said, when she was somewhat composed. "Last night about twelve o'clock."

"Twelve o'clock!" cried Tom, in surprise "Why that's about the time--"

He stopped suddenly.

"What were you going to say?" asked Mrs. Damon.

"Oh--nothing," answered Tom. "I--I'll tell you later. Go on, please."

"It is all so confusing," proceeded Mrs. Damon. "You know my husband has been in trouble of late--financial trouble?"

"Yes," responded Tom, "he mentioned it to me."

"I don't know any of the details," sighed Mrs. Damon, "but I know he was mixed up with a man named Peters."

"I know him, too," spoke Tom, grimly.

"My husband has been very gloomy of late," went on Mrs. Damon. "He foolishly entrusted almost his entire fortune to that man, and last night he told me it was probably all gone. He said he saw only the barest chance to save it, but that he was going to take that chance."

"Did he go into details?" asked Tom.

"No, that was all he said. That was about ten o'clock. He didn't want to go to bed. He just sat about, and he kept saying over and over again: 'Bless my tombstone!' 'Bless the cemetery!' and all such stuff as that. You know how he was," and she smiled through her tears.

"Yes," said Tom. "I know. Only it wasn't like him to bless such grewsome things. He was more jolly."

"He hasn't been, of late," sighed his wife. "Well, he sat about all the evening, and he kept figuring away, trying, I suppose, to find some way out of his trouble."

"Why didn't he come to my father?" cried Tom. "I told him he could have all the money he needed to tide him over."

"Well, Mr. Damon was queer that way," said his wife. "He wanted to be independent. I urged him to call you up, but he said he'd fight it out alone."

"As I said, we sat there, and he kept feeling more and more blue, and blessing his funeral, and the hearse and all such things as that. He kept looking at the clock, too, and I wondered at that."

"'Are you expecting someone?' I asked him. He said he wasn't, exactly, but I made sure he was, and finally, about half-past eleven, he put on his hat and went out."

"'Where are you going?' I asked him."

"'Oh, just to get a breath of air. I can't sleep,' he said. I didn't think much of that, as he often used to go out and walk about a bit before going to bed. So he went out, and I began to see about locking up, for I never trust the servants."

"It must have been about an hour later when I heard voices out in front. I looked, and I saw Mr. Damon talking to a man."

"Who was he?" asked Tom, eagerly, on the alert for the slightest clew.

"I thought at the time," said Mrs. Damon, "that it was one of the neighbors. I have learned since, however, that it was not. Anyhow, this man and Mr. Damon stood talking for a little while, and then they went off together. I didn't think it strange at the time, supposing he was merely strolling up and down in front with Mr. Blackson, who lives next door, He often had done that before."

"Well, I saw that the house was locked up, and then I sat down in a chair to wait for Mr. Damon to come back. I was getting sleepy, for we don't usually stay up so late. I suppose I must have dozed off, but I was suddenly awakened by hearing a peculiar noise. I sat up in alarm, and then I realized that Mr. Damon had not come in."

"I was frightened then, and I called my maid. It was nearly one o'clock, and my husband never stays out as late as that. We went next door, and found that Mr. Blackson had not been out of his house that evening. So it could not have been he to whom Mr. Damon was speaking."

"We roused up other neighbors, and they searched all about the grounds, thinking he might have been overcome by a sudden faint. But we could not find him. My husband had disappeared--mysteriously disappeared!" and the lady broke into sobs.

"Now don't worry," said Tom, soothingly, as he put his arms about her as he would have done to his own mother, had she been alive, "We'll get him back!"

"But how can you? No one knows where he is."

"Oh, yes!" said Tom, confidently, "Mr. Damon himself knows where he is, and unless he has gone away voluntarily, I think you will soon hear from him."

"What do you mean by--voluntarily?" asked the wife.

"First let me ask you a question," came from Tom. "You said you were awakened by a peculiar noise. What sort of a sound was it?"

"Why, a whirring, throbbing noise, like--like--"

She paused for a comparison.

"Like an airship?" asked Tom, with a good deal of eagerness.

"That was it!" cried Mrs. Damon. "I was trying to think where I had heard the sound before. It was just like the noise your airship makes, Tom!"

"That settles it!" exclaimed the young inventor.

"Settles what?" asked Ned.

"The manner of Mr. Damon's disappearance. He was taken away--or went away--in my airship--the airship that was stolen from my shed last night!"

Mrs. Damon stared at Tom in amazement.

"Why--why--how could that be?" she asked.

Quickly Tom told of what had happened at his place.

"I begin to see through it," he said. "There is some plot here, and we've got to get to the bottom of it. Mr. Damon either went with these men in the airship willingly, or he was taken away by force. I'm inclined to think he went of his own accord, or you would have heard some outcry, Mrs. Damon."

"Well, perhaps so," she admitted. "But would he go away in that manner without telling me?"

"He might," said Tom, willing to test his theory on all sides. "He might not have wanted you to worry, for you know you dislike him to go up an airships."

"Yes, I do. Oh, if I only thought he did go away of his own accord, I could understand it. He went, if he did, to try and save his fortune."

"It does look as though he had an appointment with someone, Tom," suggested Ned. "His looking at the clock, and then going out, and all that."

"Yes," admitted the young inventor, "and now I'm inclined to change my theory a bit. It may have been some other airship than mine that was used."

"How so?" asked Ned.

"Because the men who took mine were unprincipled fellows. Mr. Damon would not have gone away with men who would steal an airship."

"Not if he knew it," admitted Ned. "Well, then, let's consider two airships--yours and the other that came to keep the appointment with Mr. Damon. If the last is true, why should he want to go away in an airship at midnight? Why couldn't he take a train, or an auto?"

"Well, we don't know all the ins and outs," admitted Tom. "Taking a midnight airship ride is rather strange, but that may have been the only course open. We'll have to let the explanation go until later. At any rate, Mrs. Damon, I feel sure that your husband did go off through the air--either in my Eagle or in some other craft."

"Well, I'm glad to hear you say so, Tom Swift, though it sounds a dreadful thing to say. But if he did go off of his own accord, I know he did it for the best. And he may not have told me, for fear I would worry. I can understand that. But why isn't he back now?"