one afternoon, as tom was working away in the shop on his sky racer, adjusting one of the rear rudders, and pausing now and then to admire the trim little craft, he heard some one approaching. looking out through a small observation peephole made for this purpose, he saw mrs. baggert hurrying toward the building.

"i wonder what's the matter?" he said aloud, for there was a look of worriment on the lady's face. tom threw open the door. "what is it, mrs. baggert?" he called. "some one up at the house who wants to see me?"

"no, it's your father!" panted the housekeeper, for she was quite stout. "he is very ill again, and i can't seem to get dr. gladby on the telephone. central says he doesn't answer."

"my father worse!" cried tom in alarm, dropping his tools and hurrying from the shop. "where's eradicate? send him for the doctor. perhaps the wires are broken. if he can't locate dr. gladby, get dr. kurtz. we must have some one. here, rad! where are you?" he called, raising his voice.

"heah i be!" answered the colored man, coming from the direction of the garden, which he had been weeding.

"get out your mule, and go for dr. gladby. if he isn't home, get dr. kurtz. hurry, rad!"

"i's mighty sorry, massa tom," answered the colored man, "but i cain't hurry, nohow."

"why not?"

"because boomerang done gone lame, an' he won't run. i'll go mahse'f, but i cain't take dat air mule."

"never mind. i'll go in the butterfly," decided tom quickly. "i'll run up to the house and see how dad is, and while i'm gone, rad, you get out the butterfly. i can make the trip in that. if dr. kurtz had a 'phone i could get him, but he lives over on the back road, where there isn't a line. hurry, rad!"

"yes, sah, massa tom, i'll hurry!"

the colored man knew how to get the monoplane in shape for a flight, as he had often done it.

tom found his father in no immediate danger, but mr. swift had had a slight recurrence of his heart trouble, and it was thought best to have a doctor. so tom started off in his air craft, rising swiftly above the housetop, and sailed off toward the old-fashioned residence of dr. kurtz, a sturdy, elderly german physician, who sometimes attended mr. swift. tom decided that as long as dr. gladby did not answer his 'phone, he could not be at home, and this, he learned later, was the case, the physician being in a distant town on a consultation.

"my, this butterfly seems big and clumsy beside my humming-bird," mused tom as he slid along through the air, now flying high and now low, merely for practice. "this machine can go, but wait until i have my new one in the air! then i'll show 'em what speed is!"

he was soon at the physician's house, and found him in.

"won't you ride back with me in the monoplane?" asked tom. "i'm anxious to have you see dad as soon as you can.

"vot! me drust mineself in one ob dem airships? i dinks not!" exclaimed dr. kurtz ponderously. "vy, i vould not efen ride in an outer-mobile, yet, so vy should i go in von contrivance vot is efen more dangerous? no, i gomes to your fader in der carriage, mit mine old dobbin horse. dot vill not drop me to der ground, or run me up a tree, yet! vot?"

"very well," said tom, "only hurry, please."

the young inventor, in his airship, reached home some time before the slow-going doctor got there in his carriage. mr. swift was no worse, tom was glad to find, though he was evidently quite ill.

"so, ve must take goot care of him," said the doctor, when he had examined the patient. "dr. gladby he has done much for him, und i can do little more. you must dake care of yourself, herr swift, or you vill—but den, vot is der use of being gloomy-minded? i am sure you vill go more easy, und not vork so much."

"i haven't worked much," replied the aged inventor. "i have only been helping my son on a new airship."

"den dot must stop," insisted the doctor. "you must haf gomplete rest—dot's it—gomplete rest."

"we'll do just as you say, doctor," said tom. "we'll give up the aeroplane matters, dad, and go away, you and i, where we can't see a blueprint or a pattern, or hear the sound of machinery. we'll cut it all out."

"dot vould he goot," said dr. kurtz ponderously.

"no, i couldn't think of it," answered mr. swift. "i want you to go in that race, tom—and win!"

"but i'll not do it, dad, if you're going to be ill."

"he is ill now," interrupted the doctor. "very ill, dom swift."

"that settles it. i don't go in the race. you and i'll go away, dad—to california, or up in canada. we'll travel for your health."

"no! no!" insisted the old inventor gently. "i will be all right. most of the work on the monoplane is done now, isn't it, tom?"

"yes, dad."

"then you go on, and finish it. you and mr. jackson can do it without me now. i'll take a rest, doctor, but i want my son to enter that race, and, what's more, i want him to win!"

"vell, if you don't vork, dot is all i ask. i must forbid you to do any more. mit dom, dot is different. he is young und strong, und he can vork. but you—not, herr swift, or i doctor you no more." and the physician shook his big head.

"very well. i'll agree to that if tom will promise to enter the race," said the inventor.

"i will," said tom.

the physician took his leave shortly after that, the medicine he gave to mr. swift somewhat relieving him. then the young inventor, who felt in a little better spirits, went back to his workshop.

"poor dad," he mused. "he thinks more of me and this aeroplane than he does of himself. well, i will go in the race, and i'll—yes, i'll win!" and tom looked very determined.

he was about to resume work on his craft when something about the way one of the forward planes was tilted attracted his attention.

"i never left it that way," mused tom. "some one has been in here. i wonder if it was mr. jackson?"

tom stepped to the door and called for eradicate. the colored man came from the direction of the garden, which he was still weeding.

"has mr. jackson been around, rad?" asked the lad.

"no, sah. i ain't seed him."

"have you been in here, looking at the humming-bird?"

"no, massa tom. i nebber goes in dere, lessen as how yo' is dere. dem's yo' orders."

"that's so, rad. i might have known you wouldn't go in. but did you see any one enter the shop?"

"not a pusson, sab."

"have you been here all the while?"

"all but jes' a few minutes, when i went to de barn to put some liniment on boomerang's so' foot."

"h'm! some one might have slipped in here while i was away," mused tom. "i ought to have locked the doors, but i was in a hurry. this thing is getting on my nerves. i wonder if it's andy foger, or some one else, who is after my secret?"

he made a hasty examination of the shop, but could discover nothing more wrong, except that one of the planes of the humming-bird had been shifted.

"it looks as if they were trying to see how it was fastened on, and how it worked," mused tom. "but my plans haven't been touched, and no damage has been done. only i don't like to think that people have been in here. they may have stolen some of my ideas. i must keep this place locked night and day after this."

tom spent a busy week in making improvements on his craft. mr. swift was doing well, and after a consultation by dr. kurtz and dr. gladby it was decided to adopt a new style of treatment. in the meanwhile, mr. swift kept his promise, and did no work. he sat in his easy-chair, out in the garden, and dozed away, while tom visited him frequently to see if he needed anything.

"poor old dad!" mused the young inventor. "i hope he is well enough to come and see me try for the ten-thousand-dollar prize—and win it! i hope i do; but if some one builds, from my stolen plans, a machine on this model, i'll have my work cut out for me." and he gazed with pride on the humming-bird.

for the past two weeks tom had seen nothing of andy foger. the red-haired bully seemed to have dropped out of sight, and even his cronies, sam snedecker and pete bailey, did not know where he had gone.

"i hope he has gone for good," said ned newton, who lived near andy. "he's an infernal nuisance. i wish he'd never come back to shopton."

but andy was destined to come back.

one day, when tom was busy installing a wireless apparatus on his new aeroplane, he heard eradicate hurrying up the path that led to the shop.

"i wonder if dad is worse?" thought tom, that always being his first idea when he knew a summons was coming for him. quickly be opened the door.

"some one's comin' out to see you, massa tom," said the colored man.

"who is it?" asked the lad, taking the precaution to put his precious plans out of sight.

"i dunno, sah; but yo' father knows him, an' he said fo' me to come out heah, ahead ob de gen'man, an' tell yo' he were comin'. he'll be right heah."

"oh, well, if dad knows him, it's all right. let him come, rad."

"yes, sah. heah he comes." and the colored man pointed to a figure advancing down the gravel path. tom watched the stranger curiously. there was something familiar about him, and tom was sure he had met him before, yet he could not seem to place him.

"how are you, tom swift?" greeted the newcomer pleasantly. "i guess you've forgotten me, haven't you?" he held out his hand, which tom took. "don't know me, do you?" he went on.

"well, i'm afraid i've forgotten your name," admitted the lad, just a bit embarrassed. "but your face is familiar, somehow, and yet it isn't."

"i've shaved off my mustache," went on the other. "that makes a difference. but you haven't forgotten john sharp, the balloonist, whom you rescued from lake carlopa, and who helped you build the red cloud? you haven't forgotten john sharp, have you, tom?"

"well, i should say not!" cried the lad heartily. "i'm real glad to see you. what are you doing around here? come in. i've got something to show you," and he motioned to the shop where the humming-bird was housed.

"oh, i know what it is," said the veteran balloonist.

"you do?"

"yes. it's your new aeroplane. in fact, i came to see you about it."

"to see me about it?"

"yes. i'm one of the committee of arrangements for the meet to be held at eagle park, where i understand you are going to contest. i came to see how near you were ready, and to get you to make a formal entry of your machine. mr. gunmore sent me."

"oh, so you're in with them now, eh?" asked tom. "well, i'm glad to know i've got a friend on the committee. yes, my machine is getting along very well. i'll soon be ready for a trial flight. come in and look at it. i think it's a bird—a regular humming-bird!" and tom laughed.

"it certainly is something new," admitted mr. sharp as his eyes took in the details of the trim little craft. "by the way, shopton is going to be well represented at the meet."

"how is that? i thought i was the only one around here to enter an aeroplane."

"no. we have just received an entry from andy foger."

"from andy foger!" gasped tom. "is he going to try to win some of the prizes?"

"he's entered for the big one, the ten-thousand-dollar prize," replied the balloonist. "he has made formal application to be allowed to compete, and we have to accept any one who applies. why, do you object to him, tom?"

"object to him? mr. sharp, let me tell you something. some time ago a set of plans of my machine here were stolen from my house. i suspected andy foger of taking them, but i could get no proof. now you say he is building a machine to compete for the big prize. do you happen to know what style it is?"

"it's a small monoplane, something like the antoinette, his application states, though he may change it later."

"then he's stolen my ideas, and is making a craft like this!" exclaimed tom, as he sank upon a bench, and gazed from the balloonist to the humming-bird, and back to mr. sharp again. "andy foger is trying to beat me with my own machine!"