gone back home after his visit to Sam. Let's go down the street, where the Foger house is, and see if there's anything going on."

As the two lads passed the mansion, they saw a man, in the kind of suit usually worn by a carpenter, come out of the back door and stand looking across the garden. In his hand he held a saw.

"Still at the repairs, I guess," remarked Ned. "I wonder what--"

"Look there! Look! Quick!" suddenly interrupted Tom, and Ned, looking, saw someone standing behind the carpenter in the door. "If that isn't Andy Foger, I'll eat my hat!" cried Tom.

"It sure is," agreed Ned. "What in the world is he doing there?"

But his question was not answered, for, a moment later, Andy turned, and went inside, and the carpenter followed, closing the door behind them.

"That's queer," spoke Tom.

"Very," agreed Ned. "He didn't go back after all. I'd like to know what's going on in there."

"And there's someone else who would like to know, also, I think," said Tom in a low voice.

"Who?" asked Ned.

"That man hiding behind the big tree across the street. I'm sure he's watching the Foger house, and when Andy came to the door that time, I happened to look around and saw that man focus a pair of opera glasses on him and the carpenter."

"You don't mean it, Tom!" exclaimed Ned.

"I sure do. I believe that man is some sort of a spy or a detective."

"Do you think he's after Andy?"

"I don't know. Let's not get mixed up in the affair, anyhow. I don't want to be called in as a witness. I haven't the time to spare."

As if the man behind the tree was aware that he had attracted the attention of our friends, he quickly turned and walked away. Tom and Ned glanced up at the Foger house, but saw nothing, and proceeded on to the store.

"I'll wager anything that Andy has been getting in some sort of trouble in the town he moved to from here," went on Tom, "and he daren't go back. So he came here, and he's hiding in his father's old house. He could manage to live there for a while, with the carpenter bringing him in food. Say, did you notice who that man was, with the saw?"

"Yes, he's James Dillon, a carpenter who lives down on our street," replied Ned. "A nice man, too. The next time I see him, I'm going to ask him what Andy is doing in town, and what the repairs are that he's making on the house."

"Well, of course if Andy has been doing anything wrong, he wouldn't admit it," said Tom. "Though Mr. Dillon may tell you about the carpenter work. But I'm sure that man was a detective from the town where Andy moved to. You'll see."

"I don't think so," was Ned's opinion. "If Andy was hiding he wouldn't show himself as plainly as he did."

The two chums argued on this question, but could come to no decision. Then, having reached Tom's home with the bolts, they went hard at work on the airship.

"Well, now to see what happens!" exclaimed Tom the next day, when everything was ready for a trial flight. "I wish Mr. Damon was here. I sent him word, but I didn't hear from him."

"Oh, he may show up any minute," replied Ned, as he helped Tom and Koku wheel the newly-equipped airship out of the shed. "The first thing you'll hear will be him blessing something. Is this far enough out, Tom?"

"No, a little more, and then head her up into the wind. I say, Ned, if this is a success, and--"

Tom stopped suddenly and looked out into the road. Then, in a low voice, he said, to Ned:

"Don't move suddenly, or he'll suspect that we're onto his game, but turn around slowly, and look behind that big sycamore tree in front of our house Ned. Tell me what you see."

"There's a man hiding there, Tom," reported his chum, a little later, after a cautious observation.

"I thought so. What's he doing?"

"Why he--by Jove! Tom, he's looking at us through opera glasses, like that other--"

"It isn't another, it's the same fellow!" whispered Tom. "It's the spy who was watching Andy! I'm going to see what's up," and he strode rapidly toward the street, at the curb of which was the tree that partly screened the man behind it.

Chapter III Queer Repairs

Quickly Tom Swift crossed the space between the airship, that was ready for a flight, and the tree. The man behind it had apparently not seen Tom coming, being so interested in looking at the airship, which was a wonderful craft. He was taken completely by surprise as Tom, stepping up to him, asked sharply:

"Who are you and what are you doing here?"

The man started so that he nearly dropped the opera glasses, which he had held focused on the aeroplane. Then he stepped back, and eyed Tom sharply.

"What do you want?" repeated our hero. "What right have you to be spying on that airship--on these premises?" The man hesitated a moment, and then coolly returned the glasses to his pocket. He did not seem at all put out, after his first start of surprise.

"What are you doing?" Tom again asked. He looked around to see where Koku, the giant, was, and beheld the big man walking slowly toward him, for Ned had mentioned what had taken place.

"What right have you to question my actions?" asked the man, and there was in his tones a certain authority that made Tom wonder.

"Every right," retorted our hero. "That is my airship, at which you have been spying, and this is where I live."

"Oh, it is; eh?" asked the man calmly. "And that's your airship, too?"

"I invented it, and built the most of it myself. If you are interested in such things, and can assure me that you have no spying methods in view, I can show you--"

"Have you other airships?" interrupted the man quickly.

"Yes, several," answered Tom. "But I can't understand why you should be spying on me. If you don't care to accept my offer, like a gentleman, tell me who you are, and what your object is, I will have my assistant remove you. You are on private property, as this street is not a public one, being cut through by my father. I'll have Koku remove you by force, if you won't go peaceably, and I think you'll agree with me that Koku can do it. Here Koku," he called sharply, and the big man advanced quickly.

"I wouldn't do anything rash, if I were you," said the man quietly. "As for this being private property, that doesn't concern me. You're Tom Swift, aren't you; and you have several airships?"

"Yes, but what right have you to--"

"Every right!" interrupted the man, throwing back the lapel of his coat, and showing a badge. "I'm Special Agent William Whitford, of the United States Customs force, and I'd like to ask you a few questions, Tom Swift." He looked our hero full in the face.

"Customs department!" gasped Tom. "You want to ask me some questions?"

"That's it," went on the man, in a business-like voice.

"What about?"

"Smuggling by airship from Canada!"

"What!" cried Tom. "Do you mean to say you suspect me of being implicated in--"

"Now go easy," advised the man calmly. "I didn't say anything, except that I wanted to question you. If you'd like me to do it out here, why I can. But as someone might hear us--"

"Come inside," said Tom quietly, though his heart was beating in a tumult. "You may go, Koku, but stay within call," he added significantly. "Come on, Ned," and he motioned to his chum who was approaching. "This man is a custom officer and not a spy or a detective, as we thought."

"Oh, yes, I am a sort of a detective," corrected Mr. Whitford. "And I'm a spy, too, in a way, for I've been spying on you, and some other parties in town. But you may be able to explain everything," he added, as he took a seat in the library between Ned and Tom. "I only know I was sent here to do certain work, and I'm going to do it. I wanted to make some observations before you saw me, but I wasn't quite quick enough."

"Would you mind telling me what you want to know?" asked Tom, a bit impatiently. "You mentioned