Tom started the runabout forward again.

"We've got to rescue Mary!" he said to Ned, who nodded.

In another moment the two young men were lost to sight in a
swirl of smoke that swept across the street. And while they are
thus temporarily hidden may not this opportunity be taken of
telling new readers something of the hero of this story?

The young inventor was introduced in the first volume of this
series, called "Tom Swift and his Motor Cycle." It was Tom's
first venture into the realms of invention, after he had
purchased from Mr. Wakefield Damon a speedy machine that tried to
climb a tree with that excitable gentleman.

Tom, with the help of his father, an inventor of note, rebuilt
the motor cycle adding many improvements, and it served Tom in
good stead more than once.

From then on the career of Tom Swift was steadily onward and
upward. One new invention led to another from his second venture,
a motor boat, through an airship and other marvels, and
eventually to a submarine. In each of these vehicles of motion
and travel Tom and his friends, Ned Newton and Mr. Damon, had
many adventures, detailed in the respective volumes.

His venture in proceeding to save Mary Nestor from possible
danger in the blaze of the fireworks factory was not the first
time Tom had rendered service to the Nestor family. There was
that occasion on which he had sent his wireless message from
Earthquake Island, as related in an earlier volume.

Space forbids the detailing of all that had happened to the
young inventor up to the time of the opening of this story.
Sufficient to say that Tom's latest achievement had been the
recovery of treasure from the depths of the ocean.

Tom Swift's activities in connection with his inventions had
become so numerous that the Swift Construction Company, of which
Ned Newton was financial manager and Mr. Damon one of the
directors, had been formed. And when the rumor came that there
was a chance to salvage some of the untold wealth at the bottom
of the sea, Tom was interested, as were his friends.

It was decided to search for the wreck of the Pandora, sunk in
the West Indies, and one of Tom's latest submarine craft was
utilized for this purpose.

Not to go into all the details, which are given in the last
volume of this series, entitled "Tom Swift and His Undersea
Search," suffice it to say that the venture was begun. Matters
were complicated owing to the fact that Mary Nestor's uncle,
Barton Keith, was in trouble over the loss of valuable papers
proving his title to some oil lands. Mary mentioned that a
person, Dixwell Hardley, was the man who, it was supposed, was
trying to defraud her relative. And the complications may be
imagined when it is said that this same Hardley was the man who
had interested Tom in the undersea search for the riches of the
Pandora.

Tom had been at home some time now, and it was while going over
his accounts with Ned, and, incidentally, planning new
activities, that the cry of fire broke in on them.

"Whew, Tom, some heat there!" gasped Ned, lowering his arm from
his face, an action which had been necessitated by Tom's daring
in driving the car close to the blazing fireworks factory.

"I should say so!" agreed Tom. "I can almost smell the rubber
of my tires burning. But we're out of the worst of it."

"Lucky she didn't take the notion to blow up as we were
passing," grimly commented Ned. "Where are you aiming for now?"

"Mary's house. It's just beyond here. But we can't see it on
account of the smoke."

A few seconds later they had passed through the black pall that
was slashed here and there with red slivers of flame, and, coming
to a more open space, Ned and Tom cleared their eyes of smoke.

"I guess there's no immediate danger," remarked Tom, as he saw
that the home of Mary Nestor and the houses near her residence
were, for the time being, out of the path of the flames. The
explosion had blown down part of the blazing factory nearest the
residential section, and the flames had less to feed on.

But the conflagration was still a fierce one. Not half the big
factory was yet consumed, and every now and then there would
sound dull, booming reports, causing nervous screams from the
women who were out in front of their homes, while the men would
crouch down as though fearing a shower of fiery embers.

"Oh, Tom, I'm so glad you're here!" cried Mary, as the runabout
drew up in front of her home. "Do you think it will be much
worse?" and she clutched his arm, as he got down to speak to her.

"I think the worst is over, as far as you people here are
concerned," the young inventor replied. "The wind has shifted a
bit."

"And there are several engines near us, Tom," said Mr. Nestor,
coming forward. "The firemen tell me they will play streams of
water on the roofs and outsides of our houses if the flames start
this way again."

"That ought to do the trick," said Tom, with a show of
confidence. "Anybody hurt around here?" he asked. "One of the
policeman said he heard several were killed."

"They may have been--in the factory," said Mr. Nestor. "Of
course if the fire and explosions had taken place in the daytime
the loss of life would have been great. But most of the workers
had left some time before the blaze was discovered. There are a
few men on a night shift, though, and I shouldn't be surprised
but what some of them had suffered."

"Too bad!" murmured the young inventor. "You're not worried
about your home, are you, Mrs. Nestor?" he asked of Mary's
mother.

"Oh, Tom, I certainly am!" she exclaimed. "I wanted to bring
out our things, but Mr. Nestor said it wouldn't be of any use."

"Neither it would, if we've got to burn, but I don't believe we
have--now," said her husband. "That last explosion and the shift
of the wind saved us. I appreciate your coming over, Tom," he
went on. "We might have needed your help. It's queer there isn't
some better, or more effective, way of fighting a fire than just
pouring on a comparatively insignificant bit of water," he added,
as, from what was now a safe distance, they watched the firemen
using many lines of hose.

"They do have chemical extinguishers," said Ned.

"Yes, for little baby blazes that have just started," went on
Mr. Nestor. "But in all the progress of science there has not
been much advance in fighting fires. We still do as they did a
hundred years ago--squirt water on it, and mighty little of it
compared to the blaze. It would take a week to put this fire out
by the water they are using if it were not for the fact that the
blaze eats itself up and has nothing more to feed on."

"We'll have to get Tom to invent a new way of fighting fire,"
remarked Ned.

The young inventor was about to reply when several firemen,
equipped with smoke helmets which they adjusted as they ran, came
running down the street.

"What's the matter?" asked Tom of one whom he knew.

"Some men are trapped in a small shed back of the factory," was
the answer. "We just heard of it, and we're going in after them.
Oh! Oh--my--my heart!" he gasped, and he sank to the sidewalk.
Evidently he was either overcome by the smoke and poisonous gases
or by his exertions.

Tom grasped the situation instantly. Taking the smoke helmet
from the exhausted fire-fighter, the young inventor shouted:

"I'll fill your place! See if you can grab a hat, Ned, and come
on!"

One of the other firemen had two helmets, and he offered Ned
one. Pausing only long enough to see that Mr. Nestor and some
others were looking after the exhausted "smoke-eater," Ned raced
on after Tom. The two young men, following the firemen, made
their way around the end of the factory to the smoke-filled yard
in the rear. But for the helmets, which were like the gas masks
of the Great War, they would not have been able to live.

One of the firemen pointed through the luridly-lighted smoke to
a small structure near the main building. This was beginning to
burn. With quick blows of an axe the door was hewed down, and the
rescue party, including Tom and Ned, made its way inside. In the
light from the blaze, as it filtered through the windows, it
could be seen that a man lay in a huddled heap on the floor.

By motions the leader of the rescue squad made it clear that
the man was to be carried out, and Tom helped with this while
Ned, using an axe, cleared away some debris to enable the door to
be opened fully so the men could pass out carrying their burden.

The man was taken to the Nestor yard and stretched out on the
grass. Word was relayed to one of the ambulance doctors who were
on the scene attending to several injured firemen, and in a short
time the man, who, it appeared, had been overcome by smoke, was
revived.

"Well, that was a narrow squeak for you," said one of the
firemen, glad to breathe without a mask on.

"Yes, it was touch and go," remarked the young doctor, who had
used heroic measures to bring the man back from the brink of the
grave. "But you'll live now, all right."

The revived man looked dully about him. He seemed somewhat
bewildered.