"Nothing much up here," remarked Tom, when he and Ned had gone all over the second floor twice. "That scrap of paper, which put me on to the fact that some one from the Russian government had been here, is about all. They must have taken all the documents Mr. Petrofsky had."

"Maybe he didn't have any," suggested Ned.

"If he was wise he'd get rid of them when he knew he was being shadowed, as he told us. Perhaps that was why they broke up the furniture, searching for hidden papers, or they may have done it out of spite because they didn't find anything. But we might as well go downstairs and look there."

But the first floor was equally unproductive of clews, save those already noted, which showed, at least so Tom believed, that Mr. Petrofsky had been surprised and overpowered while at breakfast.

"Now for outside!" cried the young inventor. "We'll see if we can figure out how they got him away."

There were plenty of marks in the soft ground and turf, which was still damp from the night's rain, though it was now afternoon. Unfortunately, however, in approaching the house after leaving the aeroplane, Ned and Tom had not thought to exercise caution, and, not suspecting anything wrong, they had stepped on a number of footprints left by the kidnappers.

But for all that, they saw enough to convince them that several men had been at the lonely house, for there were many marks of shoes. It was out of the question, however, to tell which were those of Mr. Petrofsky and which those of his captors.

"They might have carried him out to a carriage they had in waiting," suggested Ned. "Let's go out to the front gate and look in the road. They hardly would bring the carriage up to the door."

"Good idea," commented Tom, and they hurried to the main thoroughfare that passed the Russian's house.

"Here they are!" cried Ned, Who was in the lead. "There's been a carriage here as sure as you're a foot high. and it's a rubber-tired one too."

"GOOD!" cried Tom admiringly. "You're coming right along in your detective training. How do you make that out?"

"See here, where a piece of rubber has been broken or cut out of the tire. It makes a peculiar mark in the dirt every time the wheel goes around."

"That's right, and it will be a good thing to trace the carriage by. Come on, we'll keep right after it."

"Hold on a bit," suggested Ned, who, though not so quick as Tom Swift, frequently produced good results by his very slowness. "Are you going off and leave the airship here for some one to walk off with?"

"Guess they wouldn't take it far," replied the young inventor, "but I'd better make it safe. I'll disconnect it so they can't start it, though if Andy Foger happens to come along he might slash the planes just out of spite. But I guess he won't show up."

Tom took a connecting pin out of the electrical apparatus, making it impossible to start the aeroplane, and then, wheeling it out of sight behind a small barn, he and Ned went back to the carriage marks in the road.

"Hurry!" urged Tom, as he started off in the direction of the village of Hurdtown, near where the cottage stood. "We will ask people living along the highway if they've seen a carriage pass."

"But what makes you think they went off that way?" asked Ned. "I should think they'd head away from the village, so as not to be seen."

"No, I don't agree with you. But wait, we'll look at the marks. Maybe that will help us."

Peering carefully at the marks of horses' hoofs and the wheel impressions, Tom uttered a cry of discovery.

"I have it!" he declared. "The carriage came from the village, and kept right on the other way. You're right, Ned. They didn't go back to town.

"Are you sure?"

"Of course. You can see for yourself; if the carriage had turned around the track would show, but it doesn't and, even if they turned on the grass, there'd be two lines of marks-- one coming out here and one returning. As it is there is only a single set--just as if the carriage drove up here, took on its load, and continued on. This way, Ned."

They hurried down the road, and soon came to a cluster of farm houses. Inquiries there, however, failed to bring anything to light, for either the occupants of the house had failed to notice passing vehicles, or there had been so many that any particular carriage was not recalled. And there were now so many impressions in the soft dirt of the highway--so many wheel tracks and hoof imprints--that it was impossible to pick out those of the carriage with the cut rubber tire. "Well, I guess it isn't of much use to go on any farther," spoke Ned, when they had traveled several miles and had learned nothing.

"We'll try one more house, and then go back," agreed Tom. "We'll tell dad about what's happened, and see what he says."

"Carriage?" repeated an old farmer to whom they next put the question. "Wa'al, now, come t' think of it, I did see one drivin' along here early this morning. It had rubber tires on too, for I recollect remarkin' t' myself that it didn't make much noise. Had t' talk t' myself," he added in explanation," 'cause nobody else in the family was up, 'ceptin' th' dog."

"Did the carriage have some Russians in it?" asked Tom eagerly, "and was one a big bearded man?"

"Wa'al, now you've got me," admitted the farmer frankly. "It was quite early you see, and I didn't take no particular notice. I got up early t' do my milkin' 'cause I have t' take it t' th' cheese factory. That's th' reason nobody was up but me. But I see this carriage comin' down th' road, and thinks I t' myself it was pretty middlin' early fer anybody t' be takin' a pleasure ride. I 'lowed it were a pleasure ride, 'cause it were one of them hacks that folks don't usually use 'ceptin' fer a weddin', or a funeral, an' it wa'n't no funeral."

"Then you can't tell us anything more except that it passed?" asked Ned.

"No, I couldn't see inside, 'cause it was rather dark at that hour, and then, too, I noticed that they had th' window shades down."

"That's suspicious!" exclaimed Tom. "I believe they are the fellows we re after," and, without giving any particulars he said that they were looking for a friend who might have been taken away against his will.

"Could you tell where they were going?" asked Tom, scarcely hoping to get an affirmative answer.

"Wa'al, th' man on th' seat pulled up when he see me," spoke the farmer with exasperating slowness, "an' asked me how far it was t' th' Waterville station, an' I told him."

"Why didn't you say so at first?" asked Tom quickly. "Why didn't you tell us they were heading for the railroad?"

"You didn't ask me," replied the farmer. "What difference does it make."

"Every minute counts!" exclaimed the young inventor. "We want to keep right after those fellows. Maybe the agent can tell us where they bought tickets to, and we can trace them that way.

"Shouldn't wonder," commented the farmer. There ain't many trains out from Waterville at that time of day, an' mighty few passengers. Shouldn't wonder but Jake Applesaner could put ye on th' trail."

"Much obliged," called Tom. "Come on, Ned," and he started back in the direction of the house where the kidnapping had taken place.

"That ain't th' way t' 'vaterville!" the farmer shouted after them.

"I know it, we're going to get our airship," answered Tom, and then he heard the farmer mutter.

"Plumb crazy! That's what they be! Plumb crazy! Going after their airship! Shouldn't wonder but they was escaped lunatics, and the other fellers was keepers after 'em. Hu! Wa'al, I've got my work to do. 'Tain't none of my affair."

"Let him think what he likes," commented Ned as he and his chum hurried on. "We're on the trail all right."

If Jake Applesauer, the agent at the Waterville station, was surprised at seeing two youths drop down out of an aeroplane, and begin questioning him about some suspicious strangers that had taken the morning train, he did not show it. Jake prided himself on not being surprised at anything, except once when he took a counterfeit dollar in return for a ticket, and had to make it good to the company.

But, to the despair of Tom and Ned, he could not help them much. He had seen the party, of course. They had driven up in the hack, and one of the men seemed to be sick, or hurt, for his head was done up in bandages, and the others had to half carry him on the train.

"That was Mr. Petrofsky all right," declared Ned.

"Sure," assented Tom. "They must have hurt and drugged him. But you can't tell us for what station they bought tickets, Mr. Applesauer?"

"No, for they didn't buy any. They must have had 'em, or else they paid on the train. One man drove off in the coach, and that's all I know."

As Tom and Ned started back to Shopton in the aeroplane they discussed what could be done next. A hard task lay before them, and they realized that.

"They could have gotten off at any station between here and New York, or even changed to another railroad at the junction," spoke Tom. "It's going to be a hard job."

"Guess we'll have to get some regular detectives on it," suggested Ned.

"And that's what I'll do," declared the young inventor. "They may be able to locate Mr. Petrofsky before those spies take him out of this country. If they don't--it will be too late. I'm going to talk to dad about it, and if he agrees I'll hire the best private detectives."

Mr. Swift gave his consent when Tom had told the story, and, a day later, one of the best detectives of a well known agency called on Tom in Shopton and assumed charge of the case.

The early reports from the detective were quite reassuring. He got on the trail of the men who had taken Mr. Petrofsky away, and confirmed the suspicion that they were agents of the Russian police. He trailed them as far as New York, and there the clews came to an end.

"Whether they are in the big city, which might easily be, or in some of the nearby towns, will take some time to learn," the detective wrote, and Tom wired back telling him to keep on searching.

But, as several weeks went by, and no word came, even Tom began to give up hope, though he did not stop work on the air glider, which was nearing completion. And then, most unexpectedly a clew came--a clew from far-off Russia.

Tom got a letter one day--a letter in a strange hand, the stamp and postmark showing that it had come from the land of the Czar.

"What do you suppose it contains?" asked Ned, who was with his chum when the communication was received.

"Haven't the least idea; but I'll soon find out."

"Maybe it's from the Russian police, telling you to keep away from Siberia."

"Maybe," answered Tom absently, for he was reading the missive. "I say!" he suddenly cried. "This is great! A clew at last, and from St. Petersburg! Listen to this, Ned!

"This letter is from the head of one of the secret societies over there, a society that works against the government. It says that Mr. Petrofsky is being detained a prisoner in a lonely hut on the Atlantic sea coast, not far from New York--Sandy Hook the letter says--and here are the very directions how to get there!"

"No!" cried Ned, in disbelief. "How in the world could anybody in Russia know that."

"It tells here," said Tom. "It's all explained. As soon as the secret police got Mr. Petrofsky they communicated with the head officials in St. Petersburg. You know nearly everyone is a spy over there, and the letter says that Mr. Petrofsky's friends there soon heard the news, and even about the exact place where he is being held."

"What are they holding him for?" asked Ned.

"That's explained, too. It seems they can't legally take him back until certain papers are received from his former prison in Siberia, and those are now on the way. His friends write to me to hasten and rescue him."

"But how did they ever get your address?"

"That's easy, though you wouldn't think so. It seems, so the letter explains, that as soon as Mr. Petrofsky got acquainted with us he wrote to friends in St. Petersburg, giving my address, and telling them, in case anything ever happened to him, to notify us. You see he suspected that something might, after he found he was being shadowed that way.

"And it all worked out. As soon as his friends heard that he was caught, and learned where he was being held, they wrote to me. Hurrah, Ned! A clew at last! Now to wire the detective--no, hold on, we'll go there and rescue him ourselves! We'll go in the airship, and pick up Detective Trivett in New York."

"That's the stuff! I'm with you!"

"Bless my suspender buttons! So am I, whatever it is!" cried Mr. Damon, entering the room at that moment.