"Uncle! Uncle Barton!" faltered Mary, as she clung to Mr. Keith. "Can't we get down the stairs?"

"I'm afraid not, Mary," he answered, and he closed the door of his office to keep out the smoke that was ever increasing.

"And won't the elevators come for us?"

"They don't seem able to get up," was his reply. "Probably the fire started in the bottom of the shafts, and they act just like flues, drawing up the flames and smoke."

"Then we must try the fire escapes!" exclaimed Mary, and she started toward the front window, pulling her uncle across the room after her.

"Mary, there aren't--aren't any fire escapes!" he said hoarsely.

"No fire escapes!" The girl turned paler than before.

"No, not an escape as far as I know. You see, this was thought to be a fireproof building at first and small attention was given to escapes. Then the law stepped in and the owners were ordered to put up regular escapes. They have started the work, but just now the old escapes have been torn down and the new ones are not yet in place."

"Oh, but Uncle Barton! can't we do something?" cried Mary. "There must be some way out! Let's try the elevators again, or the stairs!"

Before Mr. Keith could stop her Mary had opened the door into the hall. To the agreeable surprise of her uncle there seemed to be less smoke now.

"We may have a chance!" he cried, and he rushed out. "Hurry!"

Frantically he pushed the button that summoned the elevators. Down below, in the elevator shafts, could be heard the roar and crackle of flames.

"Let's try the stairs!" suggested Mary. "They seem to be free now."

She started down the staircase which went in square turns about the battery of elevators, and her uncle followed. But they had not more than reached the first landing when a roll of black, choking smoke, mingled with sparks of fire, surged into their faces.

"Back, Mary! Back!" cried Mr. Keith, and he dragged the impetuous girl with him to their own corridor, and back into his offices which, for the time being, were comparatively free from the choking vapor.

"We must try the windows, Uncle Barton! We must!" cried Mary. "Surely there is some way down--maybe by dropping from ledge to ledge!"

Her uncle shook his head. Then he opened the window and looked out. As he did so there arose from the streets below the cries of many voices, mingled with the various sounds of fire apparatus -- the whistles of engines, the clang of gongs, and the puffing of steamers.

"The firemen are here! They'll save us!" cried Mary, as she heard the noises in the street below. "We can leap into the life nets."

"There isn't a life net made, nor men who could retain it, to hold up a person jumping from the tenth story," said her uncle. "Our only chance is to wait for them to subdue the fire."

"Isn't there a back way down, Uncle Barton?" "No, Mary!" He closed the window for, open as it was, the draft created served to suck smoke into the office, and Mary was coughing.

Uncle and niece faced each other. Trapped indeed they were, unless the fire, which was now raging all through the building, with the stairs and elevator shafts as a center. could be subdued. That the city fire department was doing its best was not to be doubted.

"We can only wait--and hope," said Mr. Keith solemnly.

Mary gave a gasp. Her uncle thought she was going to burst into tears, but she bravely conquered herself and faced him with what was meant to be a smile. But it is difficult to smile with quivering lips, and Mary soon gave up the attempt.

Mr. Keith went over to the water cooler--one of those inverted large glass bottles--and looked to see how much water it contained.

"It's nearly full," he said.

"What good will it do?" asked Mary. "This fire is beyond a little water like that."

"Yes, but it will serve to keep our handkerchiefs wet so we can breathe through them if the smoke gets too thick," was his reply.

"It begins to look as if we'd need to try that soon," said Mary, and she pointed to thick smoke curling in under the door.

"Yes," agreed her uncle. "It's getting worse." Hardly had he spoken when there came a rush of feet in the corridor outside his office door. Then a voice exclaimed:

"We're trapped! We can't get down either the stairs or the elevators!"

"It can't be possible!" said another voice. "Something must be done! Help! Help! Take us out of here!"

"Foolish cowards!" murmured Mr. Keith, and then the door of his office was violently opened and two men rushed in. They were strangers to Mary and her uncle.

"Isn't there any way out of this fire trap?" cried one of the men. "Are there any fire escapes at your windows?"

"None," said Mr. Keith.

"This is all your fault, Melling!" cried the smaller of the two men, whose voice, in loudness and depth of pitch, was out of all proportion to his size. "All your fault! I told you we should have those new fire escapes!"

"And you were the one, Field, who objected to the cost of fire escapes when you found what the charge would be," retorted the other. "You said we didn't need to waste that money, if the building was fire-proof."

"But it isn't, Melling! It isn't!" yelled the other.

"We're finding that out too late!" came the retort. "But I'm not going to die here like a rat in a trap!" And he raised the window and leaned out and yelled, "Help! Help! Help!"

"Don't do that," said Mr. Keith, coming over to close the casement. "They can't hear you down below, and opening the window will only fill this place with smoke. Are you Field and Melling?"

"Yes, of the Consolidated Dye Company," was the answer from the big man. "We are also part owners of this building, but I wish we weren't."

"It is a pretty poor specimen of a modern building," said Mr. Keith. "You have offices here, haven't you?" he went on. "I remember to have seen your names on the directory."

"We're on the floor above," was the answer from Field. "We were in a rear room, going over some accounts, and we didn't know anything was wrong until we smelled smoke. We tried to get down, and managed to come, by way of the stairs, as far as this floor," he explained quickly.

"You can't go any farther," said Mr. Keith. "All there is to do is to wait for the firemen."

"Suppose they never come?" whined Melling. "Oh, they'll come!" asserted Mary's uncle, but he spoke more to quiet her alarm than because he really believed it, for the Landmark Building was a seething furnace of flame centering in and about the elevator shafts and stairs.

Meanwhile Tom and his companions in the airship had seen the red glow in the evening sky, and in another minute the young inventor had turned his craft more directly toward it.

"It surely is in Newmarket," said Mr. Damon. "Right in the center of the city, too. There's one big building there--the Landmark."

"Looks as if that was afire," said Ned quickly. "Hasn't some relative of Mary's an office there, Tom?"

"Yes. Mr. Keith. And her other uncle, Jasper Blake, is also interested in the building. It's the Landmark all right!" cried Tom, as his craft rose higher and advanced nearer the blaze.

"What are you going to do?" yelled Mr. Damon, as he saw the young inventor head directly toward a spouting mushroom of flame, which showed that the fire had broken through the roof. "What are you going to do?"

"Go to the rescue!" answered Tom Swift. "I couldn't ask a better opportunity to try my new extinguisher! Sit tight, every one!"