“I don’t like to doubt your word,” began Tom, slowly, “but you know, Mr. Jenks, that some of the greatest chemists have tried in vain to make diamonds; or, at best, they have made only tiny ones.  To think that any man, or set of men, made real diamonds as large as the ones you have, doesn’t seem—­well—­” and Tom hesitated.

“You mean you can hardly believe me?” asked Mr. Jenks.

“I guess that’s it,” assented Tom.

“I don’t blame you a bit!” exclaimed the odd man.  “In fact, I didn’t believe it when they told me they could make diamonds.  But they proved it to me.  I’m ready now to prove it to you.”

“I’ll tell you what I’ll do.  Here’s this one stone, cut ready for setting.  Here’s another, uncut,” and Mr. Jenks drew from his pocket what looked like a piece of crystal.  “Take them to any jeweler,” he resumed—­“to the one in whose place I saw you to-night.  I’ll abide by the verdict you get, and I’ll come here to-morrow night, and hear what you have to say.”

“Why do you come at night?” asked Tom, thinking there was something suspicious in that.

“Because my life might be in danger if I was seen talking to you, and showing you diamonds in the daytime—­especially just now.

“Why at this particular time?”

“For the reason that the diamond makers are on my trail.  As long as I remained quiet, after their shabby treatment of me, and did not try to discover their secret, they were all right.  But, after I realized that I had been cheated out of my rights, and when I began to make an investigation, with a view to discovering their secret whereabouts, I received mysterious and anonymous warnings to stop.”

“But I did not.  I came East, and tried to get help to discover the cave of the diamond makers, but I was unsuccessful.  I needed an airship, as I—­said, and no person who could operate one, would agree to go with me on the quest.  Again I received a warning to drop all search for the diamond makers, but I persisted, and about a week ago I found I was being shadowed.”

“Shadowed; by whom?” asked Tom.

“By a man I never remember seeing, but who, I have no doubt, is one of the diamond-making gang.”

“Do you think he means you harm?”

“I’m sure of it.  That is the reason I have to act so in secret, and come to see you at night.  I don’t want those scoundrels to find out what I am about to do.  On my return from Earthquake Island, I again endeavored to interest an airship man in my plan, but he evidently thought me insane.  Then I thought of you, as I had done before, but I was afraid you, too, would laugh at my proposition.  However, I decided to come here, and I did.  It seemed almost providential that my first view of you was in a jewelry shop, looking at diamonds.  I took it as a good omen.  Now it remains with you.  May I call here to-morrow night, and get your answer?”

Tom Swift made up his mind quickly.  After all it would be easy enough to find out if the diamonds were real.  If they were, he could then decide whether or not to go with Mr. Jenks on the mysterious quest.  So he answered: