almost before the echoes of eradicate's direful warning cry had died away, tom was on his way out of the house, pausing only long enough to slip on a pair of shoes and his trousers. there was but one thought in his mind. if he could get the humming-bird safely out he would not care if the shed did burn, even though it contained many valuable tools and appliances.

"we must save my new aeroplane!" thought tom, desperately. "i've got to save her!"

as he raced through the hall he caught up a portable chemical fire-extinguisher. tom saw his father's door open, and mr. swift looked out.

"what is it?" he called anxiously.

"fire!" answered the young inventor, almost before he thought of the doctor's warning that mr. swift must not be excited. tom wished he could recall the word, but it was too late. besides eradicate, down in the yard was shouting at the top of his voice:

"fire! fire! fire!"

"where, tom?" gasped mr. swift, and his son thought the aged inventor grew suddenly paler.

"aeroplane shed," answered the lad. "but don't worry dad. it's only a small blaze. we'll get it out. you stay here. we'll attend to it—mr. jackson and eradicate and i."

"no—i'm going to help!" exclaimed mr. swift, sturdily. "i'll be with you, tom. go on!"

the lad rushed down to the yard, closely followed by the engineer, who had caught up another extinguisher. eradicate was rushing about, not knowing what to do, but still keeping up his shouting.

"it's on de roof! de roof am all blazin'!" he yelled.

"quit your noise, and get to work!" cried tom. "get out a ladder, rad, and raise it to the side of the shed. then play this extinguisher on the blaze. mr. jackson, you help me run the humming-bird out. after she's safe we'll tackle the fire."

tom cast a hurried look at the burning shed. the flames were shooting high up from the roof, now, and eating their way down. as he rushed toward the big doors, which he intended to open to enable him to run out his sky racer, he was wondering how the fire came to start so high up as the roof. he wondered if a meteor could have fallen and caused it.

as the doors, which were quickly unlocked by tom, swung back, and as he and the engineer started to go in, they were met by choking fumes as if of some gas. they recoiled for the moment.

"what—what's that?" gasped tom, coughing and sneezing.

"some chemical—i—i don't know what kind," spluttered mr. jackson. "have you any carboys of acid in there tom, that might have exploded by the heat?"

"no; not a thing. let's try again."

once more they tried to go in, but were again driven back by the distressing fumes. the fire was eating down, now. there was a hole burned in the roof, and by the leaping tongues of flame tom could see his aeroplane. it was almost in the path of the blaze.

"we must get her out!" he shouted. "i'm going in!"

but it was impossible, and the daring young inventor nearly succumbed to the choking odors. mr. jackson dragged him back.

"we can't go in!" he cried. "there has been some mysterious work here! those fumes were put here to keep us from saving the machine. this fire has been set by some enemy! we can't go in!"

"but i am going!" declared tom. "we'll try the back door."

they rushed to that, but again were driven out by the gases and vapors, which were mingled with the smoke. disheartened, yet with a wild desire to do something to save his precious craft, tom swift drew back for a moment.

as he did so he heard a hiss, as eradicate turned the chemical stream on the blaze. tom looked up. the faithful colored man was on a ladder near the burning roof, acting well his part as a fireman.

"that's the stuff!" cried tom. "come on, mr. jackson. maybe if we use the chemical extinguishers we can drive out those fumes!"

the engineer understood. he took up the extinguisher he had brought, and tom got a second one from a nearby shed. then mr. swift came out bearing another.

"you shouldn't have come, dad! we can attend to it!" cried tom, fearing for the effect of the excitement on his invalid parent.

"oh, i couldn't stay there and see the shed burn. are you getting it under control? why don't you run out the humming-bird?"

tom did not mention the choking fumes. he passed up a full extinguisher to eradicate, who had used all the chemical in his. then tom got another ladder, and soon three streams were being directed on the flames. they had eaten, a pretty big hole in the roof, but the chemicals were slowly telling on them.

as soon as he saw that eradicate and mr. jackson could control the blaze, tom descended to the ground, and ran once more to the big doors. he was determined to make another try to wheel out the aeroplane, for he saw from above that the flames were now on the side wall, and might reach the craft any minute. and it would not take much to inflict serious damage on the sky racer.

"i'll get her, fumes or no fumes!" murmured tom, grimly. and, whether it was the effect of the chemical streams, or whether the choking odors were dissipated through the hole in the roof was not manifested, but, at any rate, tom found that he could go in, though he coughed and gasped for breath.

he wheeled the aeroplane outside, for the humming-bird was almost as light as her namesake. a hurried glance by the gleam of the dying fire assured tom that his craft was not damaged beyond a slight scorching of one of the wing tips.

"that was a narrow escape!" he murmured, as he wheeled the sky racer far away, out of any danger from sparks. then he went back to help fight the fire, which was extinguished in about ten minutes more.

"it was a mighty queer blaze," said mr. jackson, "starting at the top that way. i wonder what caused it?"

"we'll investigate in the morning," decided tom. "now, dad, you must get back to your room." he turned to help his father in, but at that moment mr. swift, who was trying to say something, fell over in a dead faint.

"quick! help me carry him into the house!" cried tom. "then telephone for dr. gladby, mr. jackson."

the physician looked grave when, half an hour later, he examined his patient.

"mr. swift is very much worse," he said in a low voice. "the excitement of the fire has aggravated his ailment. i would like another doctor to see him, tom."

"another doctor?" tom's voice showed his alarm.

"yes, we must have a consultation. i think dr. kurtz will be a good one to call in. i should like his opinion before i decide what course to take."

"i'll send eradicate for him at once," said the young inventor, and he went to give the colored man his instructions, while his heart was filled with a great fear for his father.