“That man—­I know him!” the young inventor exclaimed.  “It is Feldman—­the one who wanted to be changed from the trip-hammer to the airship department.  But who is that with him?”

As Tom spoke the other turned, and at the sight of his face Mary Nestor said: 

“He looks like a Frenchman, with that little mustache and imperial.”

“So he is!” exclaimed Tom, in a hoarse whisper.  “He must be the Frenchman that Eradicate spoke about.  I wonder what this can mean?  I didn’t know Feldman had left the shop.”

“You may know what you’re talking about, but I don’t, Tom,” said Mary, with a smile at her companion.  “Are they friends of yours?”

“Hardly,” spoke the young inventor dryly.  “That one, Feldman, is one of my workmen.  He had charge of a drop-forge press and trip-hammer that—­”

“Spare me the details, Tom!” interrupted Mary.  “You know I don’t understand a thing about machinery.  The wireless you erected on Earthquake Island was as much as I could comprehend.”

“Well, a trip-hammer isn’t as complicated as that,” spoke Tom, with a laugh, as he noticed that the two men were far enough away so they could not hear him.  “What I was going to say was, that one of those men works in our shops.  The other I don’t know, but I agree with you that he does look like a Frenchman, and old Eradicate had a meeting with a man whom he described as being of that nationality.”

“And you say they are not friends of yours?”

“I have no reason to believe they are.”

“Then they must be enemies!” exclaimed Mary with quick intuition.  “Oh, Tom, you will be careful, won’t you?”

“Of course I will, little girl,” he said, a note of fondness creeping into his voice, as he covered the small hand with his own large one.  “But there is no danger.”

“Then why were these men discussing you?”

“I don’t know that they were, Mary.”

“They mentioned your name.”

“Well, that may be.  Probably one of them, Feldman, who works for me, was speaking to his companion about the chance for a position.  My father and I employ a number of men, you know.”

“Well, I suppose it is all right, Tom, and I surely hope it is.  But you will be careful, won’t you?  And you look more worried than you used to.  Has anything gone wrong?”

“Not a thing, little girl.  Everything is going fine.  My new aerial warship will soon make a trial flight, and I’d be pleased to have you as a passenger.”

“Would you really, Tom?”

“Of course.  Consider that you have the first invitation.”

“That’s awfully nice of you.  But you do look worried, Tom.  Has anything troubled you?”

“No, not much.  Everything is going all right now.  We did have a little trouble at a fire in one of my buildings—­”

“A fire!  Oh, Tom!  You never told me!”

“Well, it didn’t amount to much—­the only suspicious fact about it was that it seemed to have been of incendiary origin.”