While Mr. Track, the jeweler, and several citizens, attracted by the chase after the supposed thief, are crowded into the store, anxious to hear explanations of the strange affair, I will take the opportunity to tell you something of Tom Swift, the lad who is to figure in this story.

Many of you have already made his acquaintance, when he has been speeding about in his airship or fast electric runabout, and to others we will state that our hero first made his bow to the public in the book called "Tom Swift and His Motor-Cycle," the initial volume of this series.

In that story there was related how Tom made the acquaintance of an odd individual, named Mr. Wakefield Damon, who was continually blessing himself, some part of his anatomy, or his possessions. Mr. Damon was riding a motor-cycle, and it started to climb a tree, to his pain and fright. Afterward Tom purchased the machine, and had many adventures on it, including a chase after a gang of men who had stolen a valuable patent model belonging to Mr. Swift.

Mr. Swift, and his son were both inventors. They lived together in a fine house in the suburbs of Shopton, New York, and with them dwelt Mrs. Baggert, the housekeeper (for Tom's mother was dead), and also Garret Jackson, an expert engineer, who aided the young inventor and his father in perfecting many machines.

There was also another semi-member of the household, to wit, Eradicate Sampson, an eccentric colored man, who owned a mule called Boomerang. Eradicate did odd jobs around the place, and the mule assisted his owner--that is when the mule felt like it.

In the second volume of the series, entitled "Tom Swift and His Motor-Boat," there was related the incidents following a pursuit after a gang of unprincipled men, who sought to get Possession of some of Mr. Swift's patents, and it was while in this boat that Tom, his father, and a friend, Ned Newton, rescued from Lake Carlopa a Mr. John Sharp, who fell from his burning balloon. Mr. Sharp was a skilled aeronaut, and after his recovery he joined Tom in building a big airship, called the Red Cloud. Tom's adventures in this craft are set down in detail in the third volume of the series, called "Tom Swift and His Airship." Not only did he and Mr. Sharp and Mr. Damon make a great trip, but they captured some bank robbers, and incidentally cleared themselves from the imputation of having looted the vault of seventy-five thousand dollars, which charge was fostered by a certain Mr. Foger, and his son Andy, who was Tom's enemy.

Not satisfied with having conquered the air, Tom and his father set to work to gain a victory over the ocean. They built a boat that could navigate under water, and, in the fourth book of the series, called "Tom Swift and His Submarine Boat," you will find an account of how they went under the ocean to secure a sunken treasure, and the fight they had with their enemies who sought to get it away from them. They went through many perils, not the least of which was capture by a foreign warship.

In the fifth book, entitled "Tom Swift and His Electric Runabout," there was told the story of a wonderfully speedy electric automobile the young inventor constructed, and how he made a great race in it, and saved from ruin a bank, in which his father and Mr. Damon were interested.

Tom's ability as an inventor had, by this time, become well known. One day, as related in a volume called "Tom Swift and His Wireless Message," he received a letter from a Mr. Hosmer Fenwick, of Philadelphia, asking his aid in perfecting an airship which the resident of the Quaker City had built, but which would not work. In his small monoplane, the Butterfly, Tom and Mr. Damon went to Philadelphia, as Mr. Damon was acquainted with Mr. Fenwick.

Tom carefully inspected the Whizzer which was the name of Mr. Fenwick's airship, and, after some difficulties, succeeded in getting the electric craft in shape to make a flight.

Tom, Mr. Damon and Mr. Fenwick started to make a trip to Cape May in the Whizzer, but were caught in a terrific storm, and blown out to sea. The wind became a hurricane, the airship was disabled, and wrecked in mid-air. When it fell to earth it landed on one of the small West Indian islands, but what was the terror of the three castaways to find that the island was subject to earthquake shocks.

But the earth-tremors were not the only surprise in store for Tom and his two friends, On the island they found five men and two ladies, who, by strange chance, had been stranded there when the yacht Resolute, owned by Mr. George Hosbrook, was wrecked in the same storm that disabled the airship. Mr. Hosbrook, a millionaire, was taking a party of friends to the West Indies.

When the castaways (among whom were Mr. and Mrs. Amos Nestor, parents of Mary Nestor, a girl of whom Tom was very fond) found that there was danger of the island being destroyed in an earthquake, they were in despair. There seemed no way of being rescued, as the island was out of the line of regular ship travel.

Tom, however, was resourceful. With the electrical apparatus from the wrecked airship, he built a wireless plant, and sent messages for help, broadcast over the ocean.

They were finally heard, and answered, by an operator on board the steamer Camberanian, which came on under forced draught, and rescued Tom and his friends. It was only just in time, for, no sooner had they gotten aboard the steamer in lifeboats, than the whole island was destroyed by an earthquake shock.

But Tom, the parents of Mary Nestor, Mr. Damon, Mr. Fenwick, and all the others, got safely home. Among the survivors from the yacht Resolute was a Mr. Barcoe Jenks, who now, most unexpectedly, had confronted Tom through the glass window of the jewelry store. Mr. Jenks was a peculiar man. Tom discovered this on Earthquake Island. Mr. Jenks carried with him some stones which he said were diamonds. He asserted that he had made them, but Tom did not know whether or not to believe this.

When it seemed that the castaways would not be saved Mr. Jenks offered Tom a large sum in these same diamonds for some plan whereby he might escape the earthquakes. Mr. Jenks said there was a certain secret in connection with the manufactured diamonds that he had to solve--that he had been defrauded of his rights-- and that a certain Phantom Mountain figured in it. But Tom, at that time, paid little attention to Mr. Jenks' talk. The time was to come, however, when he would attach much importance to it.

When this story opens, Tom was more interested in Mr. Barcoe Jenks than in any one else, and was wondering what he wanted to see him about. The young inventor could not quite understand how Mr. Track, the jeweler, could come back with a lad he suspected of being a thief, when the person who had acted so suspiciously, and who had knocked on the glass, was the queer man, Mr. Jenks.

"Yes, Tom I caught him," the jeweler went on. "I chased after him, and nabbed him. It was hard work, too, for I'm not a good runner. Now, you little rascal, tell me why you tried to rob my store?" and the diamond merchant shook the lad roughly.

"I--I didn't try to rob your store," was the timid answer.

"Well, perhaps you didn't, exactly, but your confederates did. Why did you rap on the glass, and why were you staring in so intently?"

"I wasn't lookin' in."

"Well, if it wasn't you, it was some one just like you. But why did you run when I raced down the street?"

"I--I don't know," and the lad began to snivel. "I--I jest ran- -that's all--'cause I see everybody else runnin', an' I thought there was a fire."

"Ha! That's a likely story! You ran because you are guilty! I'm going to hand you over to the police."

"Did he get anything, Mr. Track?" asked one of the men who had joined the jeweler in the chase.

"No, I can't say that he did. He didn't get a chance. Tom Swift was in here at the time. But this fellow was only waiting for a chance to steal, or else to aid his confederates."

"But, if he didn't take anything, I don't see how you can have him arrested," went on the man.

"On suspicion; that's how!" asserted Mr. Track. "Will some one get me a constable?"

"I wouldn't call a constable," said Tom, quietly.

"Why not?"

"Because that isn't the person who looked in your window."

"How do you know, Tom?"

"Because that person came back while you were out. I saw him."

"You saw him? Did he try to steal any of my diamonds, Tom?"

"No, I guess he doesn't need any."

"Why not?" There was wonder in the jeweler's tone.

"Why, he claims he can make all he wants."

"Make diamonds?"

"So he says."

"Why, he must be crazy!" and Mr. Track laughed.

"Perhaps he is," admitted Tom, "I'm only telling you what he says. He's the person who acted so suspiciously. He came back here, I'm telling you, while you were running down the street, and spoke to me."

"Oh, then you know him?" The jeweler's voice was suspicious.

"I didn't at first," admitted Tom. "But when he said he was Mr. Barcoe Jenks, I remembered that I had met him when I was cast away on Earthquake Island."

"And he says he can make diamonds?" asked Mr. Track.

"What did he want of you?" and the jeweler looked at Tom, quizzically.

"He wanted to have a talk with me," replied the lad, "and when he saw me in your store, he tried to attract my attention by knocking on the glass."

"That's a queer way to do," declared Mr. Track. "What did he want?"

"I don't know exactly," answered Tom, not caring to go into details just then. "But I'm sure, Mr. Track, that you've got the wrong person there. That lad never looked in the window, nor knocked on the glass."

"That's right--I didn't," asserted the captive.

The jeweler looked doubtful.

"Why did you run?" he asked.

"I told you, I thought there was a fire."

"That's right, I don't believe he's the fellow you want," put in another man. "I was standing on the corner, near White's grocery store, and I noticed this lad. That was before I heard you yelling, and saw you coming, and then I joined in the chase. I guess the man you were after got away, Track."

"He did," asserted Tom. "He came back here, a little while ago, and he ran away just now, as he heard you coming."

"Where did he go?" asked the jeweler, eagerly.

"I don't know," answered Tom. "Only you've got the wrong lad here."

"Well, perhaps I have," admitted the diamond merchant. "You can go, youngster, but next time, don't run if you're not guilty."

"I thought there was a fire," repeated the lad, as he hurriedly slipped through the crowd in the store, and disappeared down the dark street.

"Well, I guess the excitement's all over, and, anyhow, you weren't robbed, Track," said a stout man, as he left the store. The others soon followed, and Tom and the jeweler were once more alone in the shop.

"Can you tell me something about this man, Tom?" asked Mr. Track, eagerly. "So he really makes diamonds. Who is he?"

"I'd rather not tell--just now," replied the young inventor. "I don't take much stock in him, myself. I think he's visionary. He may think he has made diamonds, and he may have made some stones that look like them. I'm very skeptical."

"If you could bring me some, Tom, I could soon tell whether they were real or not. Can you?"

The lad shook his head.

"I don't expect to see Mr. Jenks again," he said. "He talked rather wildly about waiting to meet me, but that man is odd-- crazy, perhaps--and I don't imagine I'll see him. He's harmless, but he's eccentric. Well, there was quite some excitement for a time."

"I should say there was. I thought it was a plan to rob me," and the jeweler began putting away the diamond pins. In fact, the excitement so filled the minds of himself and Tom that neither of them thought any more of the object of the lad's visit, and the young inventor departed without purchasing the pin he had come after.

It was not until he was out on the street, walking toward his home, that the matter came back to his mind.

"I declare!" he exclaimed. "I didn't get that pin for Mary, after all! Well, never mind, I have a week until her birthday, and I can get it toÄmorrow."

He walked rapidly toward home, for the weather looked threatening, and Tom had no umbrella. He was musing on the happenings of the evening when he reached his house. His father was out, as was Garret Jackson, the engineer; and Mrs. Baggert, the housekeeper, was entertaining a lady in the sitting-room, so, as Tom was rather tired, he went directly to his own room, and, a little later got into bed.

It was shortly after midnight when he was awakened by hearing a rattling on the window of his room. The reason he was able to fix the time so accurately was because as soon as he awakened he pressed a little electric button, and it illuminated the face of a small clock on his bureau. The hands pointed to five minutes past twelve.

"Humph! That sounds like hail!" exclaimed Tom, as he arose, and looked out of the casement. "I wonder if any of the skylights of the airship shed are open? There might be some damage. Guess I'd better go out and take a look."

He had mentally reasoned this far before he had looked out, and when he saw that the moon was brightly shining in a clear sky, he was a bit surprised.

"Why-Äthat wasn't hail," he murmured. "It isn't even raining. I wonder what it was?"

He was answered a moment later, for a shower of fine gravel from the walk flew up and clattered against the glass. With a start, Tom looked down, and saw a dark figure standing under an apple tree.

"Hello! Who's there?" called the lad, after he had raised the sash.

"It's I--Mr. Jenks," was the surprising answer.

"Mr. Jenks?" repeated Tom.

"Yes--Barcoe Jenks, of Earthquake Island."

"You here? What do you want?"

"Can you come down?"

"What for?"

"Tom Swift, I've something very important to tell you," was the answer in a low voice, yet which carried to Tom's ears perfectly. "Do you want to make a fortune for yourself--and for me?"

"How?" Tom was beginning to think more and more that Mr. Jenks was crazy.

"How? By helping me to discover the secret of Phantom Mountain, where the diamonds are made! Will you?"

"Wait a minute--I'll come down," answered Tom, and he began to grope for his clothes in the dim light of the little electric lamp.

What was the secret of Phantom Mountain? What did Mr. Jenks really want? Could he make diamonds? Tom asked himself these questions as he hastily dressed to go down to his midnight visitor.