For a few moments after the custom officer had made his appeal, Tom Swift did not reply. His thoughts were busy with many things. Somehow, it seemed of late, there had been many demands on him, demands that had been hard and trying.

In the past he had not hesitated, but in those cases friendship, as well as a desire for adventures, had urged him. Now he thought he had had his fill of adventures.

"Well?" asked Mr. Whitford, gently. "What's your answer, Tom? Don't you think this is a sort of duty-call to you?"

"A duty-call?" repeated the young inventor.

"Yes. Of course I realize that it isn't like a soldier's call to battle, but Uncle Sam needs you just the same. When there is a war the soldiers are called on to repel an enemy. Now the smugglers are just as much an enemy of the United States, in a certain way, as an armed invader would be."

"One strikes at the life and liberty of the people, while the smugglers try to cheat Uncle Sam out of money that is due him. I'm not going to enter into a discussion as to the right of the government to impose duties. People have their own opinion as to that. But, as long as the law says certain duties are to be collected, it is the duty of every citizen, not only to pay those dues, but to help collect them. That's what I'm asking you to do, Tom."

"I don't want to get prosy, or deliver a lecture on the work of the custom house, Tom, but, honestly, I think it is a duty you owe to your country to help catch these smugglers. I admit I'm at the end of my rope. This last clew has failed. The Fogers seem to be innocent of wrong doing. We need your help, Tom."

"But I don't see how I can help you."

"Of course you can! You're an expert with airships. The smugglers are using airships, of that I'm sure. You tell me you have just perfected a noiseless aircraft. That will be just the thing. You can hover on the border, near the line dividing New York State from Canada, or near the St. Lawrence, which is the natural division for a certain distance, and when you see an airship coming along you can slip up in your noiseless one, overhaul it, and make them submit to a search."

"But I won't have any authority to do that," objected Tom, who really did not care for the commission.

"Oh, I'll see that you get the proper authority all right," said Mr. Whitford significantly. "I made you a temporary deputy to-night, but if you'll undertake this work, to catch the smugglers in their airships, you will be made a regular custom official."

"Yes, but supposing I can't catch them?" interposed our hero. "They may have very fast airships, and--"

"I guess you'll catch 'em all right!" put in Ned, who was at his chum's side as they walked along a quiet Shopton street in the darkness. "There's not an aeroplane going that can beat yours, Tom."

"Well, perhaps I could get them," admitted the young inventor. "But--"

"Then you'll undertake this work for Uncle Sam?" interrupted Mr. Whitford eagerly. "Come, Tom, I know you will."

"I'm not so sure of that," spoke Tom. "It isn't going to be as easy as you think. There are many difficulties in the way. In the first place the smuggling may be done over such a wide area that it would need a whole fleet of airships to capture even one of the others, for they might choose a most unfrequented place to cross the border."

"Oh, we would be in communication with you," said the agent. "We can come pretty near telling where the contrabrand goods will be shipped from, but the trouble is, after we get our tips, we can't get to the place before they have flown away. But with your airship, you could catch them, after we sent you, say a wireless message, about where to look for them. So that's no objection. You have a wireless outfit on your airships, haven't you, Tom?"

"Yes, that part is all right."

"Then you can't have any more objections, Tom."

"Well, there are some. For instance you say most of this smuggling is done at night."

"Practically all of it, yes."

"Well, it isn't going to be easy to pick out a contraband airship in the dark, and chase it. But I'll tell you what I'll do, Mr. Whitford, I feel as if I had sort of 'fallen down' on this clew business, as the newspaper men say, and I owe it to you to make good in some way."

"That's what I want--not that I think you haven't done all you could," interposed the agent.

"Well, if I can figure out some way, by which I think I can come anywhere near catching these smugglers, I'll undertake the work!" exclaimed Tom. "I'll do it as a duty to Uncle Sam, and I don't want any reward except my expenses. It's going to cost considerable, but--"

"Don't mind the expense!" interrupted Mr. Whitford. "Uncle Sam will stand that. Why, the government is losing thousands of dollars every week. It's a big leak, and must be stopped, and you're the one to stop it, Tom."

"Well, I'll try. I'll see you in a couple of days, and let you know if I have formed any plan. Now come on, Ned. I'm tired and want to get to bed."

"So do I," added the agent. "I'll call on you day after to-morrow, Tom, and I expect you to get right on the job," he added with a laugh.

"Have you any idea what you are going to do, Tom?" asked his chum, as they turned toward their houses.

"Not exactly. If I go I'll use my noiseless airship. That will come in handy. But this night business rather stumps me. I don't quite see my way to get around that. Of course I could use an ordinary searchlight, but that doesn't give a bright enough beam, or carry far enough. It's going to be quite a problem and I've got to think it over."

"Queer about the Fogers; wasn't it, Tom?"

"Yes, I didn't think they were going to let us in."

"There's something going on there, in spite of the fact that they were willing for an inspection to be made," went on Ned.

"I agree with you. I thought it was funny the way Mr. Foger acted about not wanting the men to go down in the cellar."

"So did I, and yet when they got down there they didn't find anything."

"That's so. Well, maybe we're on the wrong track, after all. But I'm going to keep my eyes open. I don't see what Andy wants with an airship platform on the roof of his house. The ground is good enough to start from and land on."

"I should think so, too. But then Andy always did like to show off, and do things different from anybody else. Maybe it's that way now."

"Perhaps," agreed Tom. "Well, here's your house, Ned. Come over in the morning," and, with a good-night, our hero left his chum, proceeding on toward his own home.

"Why, Koku, haven't you gone to bed yet?" asked the young inventor, as, mounting the side steps, he saw his giant servant sitting there on a bench he had made especially for his own use, as ordinary chairs were not substantial enough. "What is the matter?"

"Nothing happen yet," spoke Koku significantly, "but maybe he come pretty soon, and then I get him."

"Get who, Koku?" asked Tom, with quick suspicion.

"I do not know, but Eradicate say he hear someone sneaking around his chicken coop, and I think maybe it be same man who was here once before."

"Oh, you mean the rivals, who were trying to get my moving picture camera?"

"That's what!" exclaimed Koku.

"Hum!" mused Tom. "I must be on the look-out. I'll tell you what I'll do, Koku. I'll set my automatic camera to take the moving pictures of any one who tries to get in my shop, or in the chicken coop. I'll also set the burglar alarm. But you may also stay on the watch, and if anything happens--"

"If anything happens, I will un-happen him!" exclaimed the giant, brandishing a big club he had beside him.

"All right," laughed Tom. "I'm sleepy, and I'm going to bed, but I'll set the automatic camera, and fix it with fuse flashlights, so they will go off if the locks are even touched."

This Tom did, fixing up the wizard camera, which I have told you about in the book bearing that title. It would take moving pictures automatically, once Tom had set the mechanism to unreel the films back of the shutter and lens. The lights would instantly flash, when the electrical connections on the door locks were tampered with, and the pictures would be taken.

Then Tom set the burglar alarm, and, before going to bed he focused a searchlight, from one of his airships, on the shed and chicken coop, fastening it outside his room window.

"There!" he exclaimed, as he got ready to turn in, not having awakened the rest of the household, "when the burglar alarm goes off, if it does, it will also start the searchlight, and I'll get a view of who the chicken thief is. I'll also get some pictures."

Then, thinking over the events of the evening, and wondering if he would succeed in his fight with the smugglers, providing he undertook it, Tom fell asleep.

It must have been some time after midnight that he was awakened by the violent ringing of a bell at his ear. At first he thought it was the call to breakfast, and he leaped from bed crying out:

"Yes, Mrs. Baggert, I'm coming!"

A moment later he realized what it was.

"The burglar alarm!" he cried. "Koku, are you there? Someone is trying to get into the chicken coop!" for a glance at the automatic indicator, in connection with the alarm, had shown Tom that the henhouse, and not his shop, had been the object of attack.

"I here!" cried Koku, "I got him!"

A series of startled cries bore eloquent testimony to this.

"I'm coming!" cried Tom. And then he saw a wonderful sight. The whole garden, his shop, the henhouse and all the surrounding territory was lighted up with a radiance almost like daylight. The beams of illumination came from the searchlight Tom had fixed outside his window, but never before had the lantern given such a glow.

"That's wonderful!" cried Tom, as he ran to examine it. "What has happened? I never had such a powerful beam before. There must be something that I have stumbled on by accident. Say, that is a light all right! Why it goes for miles and miles, and I never projected a beam as far as this before."

As Tom looked into a circle of violet-colored glass set in the side cf the small searchlight, to see what had caused the extraordinary glow, he could observe nothing out of the ordinary. The violet glass was to protect the eyes from the glare.

"It must be that, by accident, I made some new connection at the dynamo," murmured Tom.

"Hi! Lemme go! Lemme go, Massa giant! I ain't done nuffin'!" yelled a voice.

"I got you!" cried Koku.

"It's an ordinary chicken thief this time I guess," said Tom. "But this light--this great searchlight--"

Then a sudden thought came to him.

"By Jove!" he cried. "If I can find out the secret of how I happened to project such a beam, it will be the very thing to focus on the smugglers from my noiseless airship! That's what I need--a searchlight such as never before has been made--a terrifically powerful one. And I've got it, if I can only find out just how it happened. I've got to look before the current dies out."

Leaving the brilliant beams on in full blast, Tom ran down the stairs to get to his shop, from which the electrical power came.