Tom Swift hardly knew what to think. He had scarcely believed, in spite of the fact that he was sure Andy had a copy of the map, that the bully would actually make an effort to go to the valley of gold.

"And in that airship of his, too," mused Tom. "Well, there's one consolation, I don't believe he'll go far in that, though it does sail better than when he made his first attempt. Well, if he's going to try to beat us, it's a good thing I know it We can be prepared for him, now."

Tom, after watching the big vans for a few minutes, turned and kept on toward his home.

There was more than surprise on the part of Mr. Damon and the others when Tom told his news. There was alarm, for there was a feeling that Mr. Foger and his son might adopt unscrupulous tricks.

"But what can we do?" asked Mr. Swift

"Whitewash him!" exclaimed Eradicate Sampson, who had overheard part of the conversation. "Dat's what I'd do t' him an' his father, too! Dat's what I would! Fust I'd let mah mule Boomerang kick him a bit, an' den, when he was all mussed up, I'd whitewash him!" That was the colored man's favorite method of dealing with enemies, but, of course, he could not always carry it out.

However, after considering the matter from all sides, it was decided that nothing could be done for the present.

"Let them go," said Tom, "I don't believe they'll ever find the valley of gold. I fancy I threw a scare into Andy, talking as I did about the map."

"Well, even if the Fogers do get the gold," said Mr. Parker calmly, "they cannot take away the caves of ice, and it is in them that I am most interested. I want to prove some of my new theories."

"And we need the gold," said Tom, in a low voice; "don't we, Abe?"

"That's what we do, Tom," answered the old miner.

Preparations were now practically completed for their trip to Seattle by rail. Tom made some inquiries in the next few days regarding the Fogers, but only learned that the father and son had left town, after superintending the shipment of their airship.

"Well, we start to-day," remarked Tom, as he arose one morning. "In two weeks, at most, we ought to be hovering over the valley, Abe."

"I hope so? Tom. You've got the map put away safely, have you?"

"Sure thing. Are you all ready?"

"Yes."

"Then we'll start for the depot right after breakfast." The adventurers had arranged to take a local train from Shopton, and get on a fast express at one of the more important! stations.

Good-byes were said, Mr. Swift, Mr. Jackson, Mrs. Baggert and Eradicate waving their adieus from the porch as Tom and the others started for the depot. Miss Mary Nestor had bidden our hero farewell the previous night--it being a sort of second good-bye, for Tom was a frequent caller at her house, and, if the truth must be told he rather disliked to leave the young lady.

Tom found a few of his friends at the station, who had gathered there to give him and Ned bon-voyage.

"Bring us back some nuggets, Tom," pleaded Arthur Norton.

"Bring me a musk-ox if you can shoot one," suggested one.

"A live bear or a trained Eskimo for mine," exclaimed another.

Tom laughingly promised to do the best he could.

"I'll send you some gold nuggets by wireless," said Ned Newton.

It was almost time for the train to arrive. In the crowd on the platform Tom noticed Pete Bailey.

"He must feel lost without Andy," observed the young inventor to Ned.

"Yes, I wonder what he's hanging around here for?"

They learned a moment later, for they saw Pete going into the telegraph office.

"Must be something important for him to wire about," observed Ned.

Tom did not answer. The window of the office was slightly open, though the day was cool, and he was listening to the clicks of the telegraph instrument, as the operator sent Pete's message. Tom was familiar with the Morse code. What was his surprise to hear the message being sent to Andy Foger at a certain hotel in Chicago. And the message read:

"Tom Swift's party leaving to-day."

"What in the world does that mean?" thought Tom, but he did not tell Ned what he had picked up as it went over the wire. "Why should Andy want to be informed when we leave? That's why Pete was hanging around here! He had been instructed to let Andy know when we left for Seattle. There's something queer back of all this."

Tom was still puzzling over the matter when their train roiled in and he and the others got aboard.

"Well, we're off!" cried Ned.

"Yes; we're off," admitted Tom, and, to himself he added: "No telling what will happen before we get there, though."

The trip to Chicago was without incident, and, on arrival in the Windy City, Tom was on the lookout for Andy or his father, but he did not see them. He made private inquiries at the hotel mentioned in Pete's telegram, but learned that the Fogers had gone on.

"Perhaps I'm worrying too much," thought Tom. But an event that occurred a few nights later, when they were speeding across the continent showed him that there was need of great precaution.

On leaving Chicago, Tom had noticed, among the other passengers traveling in the same coach as themselves, a man who seemed to be closely observing each member of the party of gold-hunters. He was a man with a black mustache, a mustache so black, in fact, that Tom at once concluded that it had been dyed. This, in itself, was not much, but there was a certain air about the man--a "sporty" air--which made Tom suspicious.

"I wouldn't be surprised if that man was a gambler, Ned," he said to his chum, one afternoon, as they were speeding along. The man in question was several seats away from Tom.

"He does look like one," agreed Ned.

"I needn't advise you not to fall in with any of his invitations to play cards, I suppose," went on Tom, after a pause.

"No, indeed, it's something I don't do," answered Ned, with a laugh. "But it might be a good thing to speak to Abe Abercrombie about him. If that man's a sharper perhaps Abe knows him, or has seen him, for Abe has traveled around in the West considerable."

"We'll ask him," agreed Tom, but the miner, when his attention was called to the man, said he had never seen him before.

"He does look like a confidence man," agreed Abe, "but as long as he doesn't approach us we can't do anything, and don't need to worry."

There was little need to call the attention of either Mr. Damon or Mr. Parker to the man, for Mr. Damon was busy watching the scenery, as this trip was a new one to him, and he was continually blessing something he saw or thought of. As for Mr. Parker, he was puzzling over some new theories he had in mind, and he said little to the others.

On the night of the same day on which Tom had called special attention to the man with the black mustache, our hero went to his berth rather late. He had sent some telegrams to his father and one to Miss Nestor, and, when he turned in he saw the "gambler," as he had come to call him, going into the smoking compartment of the coach. Though Tom thought of the man as a gambler, there was no evidence, as yet, that he was one, and he had made no effort to approach any of our friends, though he had observed them closely.

How long Tom had been asleep he did not know, but he was suddenly awakened by feeling his pillow move. At first he thought it was caused by the swaying of the train, and he was about to go to sleep again, when there came a movement that he knew could not have been caused by any unevenness of the roadbed.

Then, like a flash there came to Tom's mind the thought that under his pillow, in a little leather case he had made for it, was the map, showing the location of the valley of gold.

He sat up suddenly, and made a lunge for the pillow. He felt a hand being hurriedly withdrawn. Tom made a grab for it, but the fingers slipped from his grasp.

"Here! Who are you!" cried Tom, endeavoring to peer through the darkness.

"It's all right--mistake," murmured a voice.

Tom leaned suddenly forward and parted the curtains of his berth. There was a dim light burning in the aisle of the car. By the gleam of it the young inventor caught sight of a man hurrying away, and he felt sure the fellow who had put his hand under his pillow was the man with the black mustache. He confirmed this suspicion a moment later, for the man half turned, as if to look back, and the youth saw the mustache.

"He--he was after my map!" thought Tom, with a gasp.

He sat bolt upright. What should he do? To raise an alarm now, he felt, would only bring a denial from the man if he accused him. There might also be a scene, and the man might get very indignant. Then, too, Tom and his friends did not want their object made known, as it would be in the event of Tom raising an outcry and stating what was under his pillow.

He felt for the map case, opened it and saw, in the gleam of the light, that it was safe.

"He didn't get it anyhow," murmured our hero. "I guess I won't say anything until morning, though he did come like a thief in the night to see if he could steal it."

Tom glanced to where his coat and other clothing hung in the little berth-hammock, and a hasty search showed that his money and ticket were safe.

"It was the map he was after all right," mused Tom. "I'll have a talk with Mr. Damon in the morning about what's best to do. That's why the fellow has been keeping such a close watch on us. He wanted to see who had the map."

Then another thought came to Tom.

"If it was the map he was after," he whispered to himself, "he must know what it's about Therefore the Fogers must have told him. I'll wager Andy or his father put this man up to steal the map. Andy's afraid he hasn't got a copy of the right one. This is getting more and more mysterious! We must be on our guard all the while. Well, I'll see what I'll do in the morning."

But in the morning the man with the black mustache was not aboard the train, and on inquiring of the conductor, Tom learned that the mysterious stranger had gotten off at a way station shortly after midnight.