"Who was it?" asked Mr. Gunmore as Tom again entered the library. "A friend of yours?"

"Hardly a friend," replied Tom grimly. "It was a young fellow who has made lots of trouble for me in the past, and who, lately, with his father, tried to get ahead of me and some friends of mine in locating a gold claim in Alaska. I don't know what he's up to now, but certainly it wasn't any good. He's got nerve, sneaking up under our windows!"

"What do you think was his object?"

"It would he hard to say."

"Can't you find him to-morrow, and ask him?"

"There's not much satisfaction in that. The less I have to do with Andy Foger the better I'm satisfied. Well, perhaps it's just as well I fell, and couldn't catch him. There would have been a fight, and I don't want to worry dad any more than I can help. He hasn't been very well of late."

"No, he doesn't look very strong," agreed the secretary. "But I hope he doesn't get sick, and I hope no bad consequences result from the eavesdropping of this Foger fellow."

Tom started for the hall, to get a brush with which to remove some of the dust gathered in his chase after Andy. As he opened the library door to go out Mr. Swift came in again.

"I saw Mrs. Baggert, Tom," he said. "She wasn't out under the window, and, as you said, Eradicate isn't about. His mule is in the barn, so it couldn't have been the animal straying around."

"No, dad. It was Andy Foger."

"Andy Foger!"

"Yes. I couldn't catch him. But you'd better go lie down, father. It's getting late, and you look tired."

"I am tired, Tom, and I think I'll go to bed. Have you finished your arrangements with Mr. Gunmore?"

"Well, I guess we've gone as far as we can until I invent the new aeroplane," replied Tom, with a smile.

"Then you'll really enter the meet?" asked the secretary eagerly.

"I think I will," decided Tom. "The prize of ten thousand dollars is worth trying for, and besides that, I'll be glad to get to work again on a speedy craft. Yes, I'll enter the meet."

"Good!" exclaimed Mr. Gunmore, shaking hands with the young inventor. "I didn't have my trip for nothing, then. I'll go back in the morning and report to the committee that I've been successful. I am greatly obliged to you."

He left the Swift home, after refusing Tom's invitation to remain all night, and went to his hotel. Tom then insisted that his father retire.

As for the young inventor, he was not satisfied with the result of his attempt to catch Andy Foger. He had no idea why the bully was hiding under the library window, but Tom surmised that some mischief might be afoot.

"Sam Snedecker or Pete Bailey, the two cronies of Andy, may still be around here, trying to play some trick on me," mused Tom. "I think I'll take a look outside." And taking a stout cane from the umbrella rack, the youth sallied forth into the yard and extensive grounds surrounding his house.

While he is thus looking for possible intruders we will tell you a little more about him than has been possible since the call of the aviation secretary.

Tom Swift lived with his father, Barton Swift, in the town of Shopton, New York State. The young man had followed in the footsteps of his parent, and was already an inventor of note.

Their home was presided over by Mrs. Baggert, as housekeeper, since Mrs. Swift had been dead several years. In addition, there was Garret Jackson, an engineer, who aided Tom and his father, and Eradicate Sampson, an odd colored man, who, with his mule, Boomerang, worked about the place.

In the first volume of this series, entitled "Tom Swift and his Motor-Cycle," here was related how he came to possess that machine. A certain Mr. Wakefield Damon, an eccentric gentleman, who was always blessing himself, or something about him, owned the cycle, but he came to grief on it, and sold it to Tom very cheaply.

Tom had a number of adventures on the wheel, and, after having used the motor to save a valuable patent model from a gang of unscrupulous men, the lad acquired possession of a power boat, in which he made several trips, and took part in many exciting happenings.

Some time later, in company with John Sharp, an aeronaut, whom Tom had rescued from Lake Carlopa, after the airman had nearly lost his life in a burning balloon, the young inventor made a big airship, called the Red Cloud. With Mr. Damon, Tom made several trips in this craft, as set forth in the book, "Tom Swift and His Airship."

It was after this that Tom and his father built a submarine boat, and went under the ocean for sunken treasure, and, following that trip Tom built a speedy electric runabout, and by a remarkable run in that, with Mr. Damon, saved a bank from ruin, bringing gold in time to stave off a panic.

"Tom Swift and His Wireless Message" told of the young inventor's plan to save the castaways of Earthquake Island, and how he accomplished it by constructing a wireless plant from the remains of the wrecked airship Whizzer. After Tom got back from Earthquake Island he went with Mr. Barcoe Jenks, whom he met on the ill-fated bit of land, to discover the secret of the diamond makers. They found the mysterious men, but the trip was not entirely successful, for the mountain containing the cave where the diamonds were made was destroyed by a lightning shock, just as Mr. Parker, a celebrated scientist, who accompanied the party, said it would be.

But his adventure in seeking to discover the secret of making precious stones did not satisfy Tom Swift, and when he and his friends got back from the mountains they prepared to go to Alaska to search for gold in the caves of ice. They were almost defeated in their purpose by the actions of Andy Foger and his father, who in an under-hand manner, got possession of a valuable map, showing the location of the gold, and made a copy of the drawing.

Then, when Tom and his friends set off in the Red Cloud, as related in "Tom Swift in the Caves of Ice," the Fogers, in another airship, did likewise. But Tom and his party were first on the scene, and accomplished their purpose, though they had to fight the savage Indians. The airship was wrecked in a cave of ice, that collapsed on it, and the survivors had desperate work getting away from the frozen North.

Tom had been home all the following winter and spring, and he had done little more than work on some small inventions, when a new turn was given his thoughts and energies by a visit from Mr. Gunmore, as narrated in the first chapter of the present volume.

"Well, I guess no one is here," remarked the young inventor as he completed the circuit of the grounds and walked slowly back toward the house. "I think I scared Andy so that he won't come back right away. He had the laugh on me, though, when I stumbled and fell."

As Tom proceeded he heard some one approaching, around the path at the side of the house.

"Who's there?" he called quickly, taking a firmer grasp of his stick,

"It's me, Massa Swift," was the response. "I jest come back from town. I got some peppermint fo' mah mule, Boomerang, dat's what I got."

"Oh! It's you, is it, Rad?" asked the youth in easier tones.

"Dat's who it am, Did yo' t'ink it were some un else?"

"I did," replied Tom. "Andy Foger has been sneaking around. Keep your eyes open the rest of the night, Rad."

"I will, Massa Tom."

The youth went into the house, having left word with the engineer, Mr. Jackson, to be on the alert for anything suspicious.

"And now I guess I'll go to bed, and make an early start to-morrow morning, planning my new aeroplane," mused Tom. "I'm going to make the speediest craft of the air ever seen!"

As he started toward his room Tom Swift heard the voice of the housekeeper calling to him:

"Tom! Oh, Tom! Come here, quickly!"

"What's the matter?" he asked, in vague alarm.

"Something has happened to your father!" was the startling reply. "He's fallen down, and is Unconscious! Come quickly! Send for the doctor!"

Tom fairly ran toward his father's room.