“Know you—­you?” repeated the lad.

“Yes—­don’t you remember Earthquake Island—­how we were nearly killed there—­don’t you remember Mr. Jenks?”

“Mr. Jenks?”

Tom was so startled that he could only repeat words after the strange man, who was talking to him from outside the glass door.

“Yes, Mr. Jenks,” was the reply.  “Mr. Barcoe Jenks, who makes diamonds.  I saw you in the store about to buy a diamond—­I wanted to tell you not to—­I’ll give you a better diamond than you can buy—­I just arrived in this place—­I must have a private talk with you—­Come out—­I’ll share a wonderful secret with you.”

A flood of memory came to Tom.  He did recall the very strange man who walked around Earthquake Island—­where Tom and some friends had been marooned recently—­walked about with a pocketful of what he said were diamonds.  Now Barcoe Jenks was here.

“I must see you privately, Tom Swift,” went on Mr. Jenks, as he once more tapped on the glass.  “Don’t waste money buying diamonds, when you and I can make better ones.  Where can I have a talk with you?  I—­” Mr. Jenks suddenly looked down the dimly-lighted street.  “They’re coming back!” he cried.  “I don’t want to be seen.  I’ll call at your house later to-night—­be on the watch for me—­until then—­good-by!”

He waved his hand, and was gone in an instant.  Tom stood staring at the glass door.  He hardly knew whether to believe it or not—­perhaps it was all a dream.

He pinched himself to make sure that he was awake.  Very substantial flesh met his thumb and finger, and he felt the pain.

“I’m awake all right,” he murmured.  “But Barcoe Jenks here—­and still talking that nonsense about his manufactured diamonds.  I think he must be crazy.  I wonder—­”

Once more the lad’s musing was interrupted.  He heard a murmur of excited voices outside the store, on the street.  Then the door of the jewelry shop was tried.  Mr. Track’s face was pressed against the glass.

“Open the door!  Let me in, Tom!” he called.  “I’ve caught the thief,” and as the lad unlocked the portal he saw that the jeweler held by the arm a ragged lad.  “Ah; you scoundrel!  I’ve caught you!” cried the diamond merchant, shaking the small chap, while Tom looked on, more mystified than ever.

CHAPTER II—­A MIDNIGHT VISIT

While Mr. Track, the jeweler, and several citizens, attracted by the chase after the supposed thief, are crowded into the store, anxious to hear explanations of the strange affair, I will take the opportunity to tell you something of Tom Swift, the lad who is to figure in this story.

Many of you have already made his acquaintance, when he has been speeding about in his airship or fast electric runabout, and to others we will state that our hero first made his bow to the public in the book called “Tom Swift and His Motor-Cycle,” the initial volume of this series.