air, except to
sell you a good stone, But if this brooch is for a young lady, I can't
recommend anything nicer. Do you think you will take this; or do you
prefer to look at some others?"

"Oh, I think this will do, Mr. Track. I guess I'll take--"

Tom's Words were interrupted by a sudden action on the part of the
jeweler. Mr. Track ran from behind the showcase and hastened toward the
front door.

"Did you see him, Tom?" he cried. "I wonder which way he went?"

"Who?" asked the lad, following the shopkeeper.

"That man. He's been walking up and down in front of my place for the
last ten minutes--ever since you've been in here, in fact, and I don't
like his looks."

"What did he do?"

"Nothing much, except to stare in here as if he was sizing my place up."

"Sizing it up?"

"Yes. Getting the lay of the land, so he or some confederate could
commit a robbery, maybe."

"A robbery? Do you think that man was a thief?"

"I don't know that he was, Tom, and yet a jeweler has to be always
on the watch, and that isn't a joke, either, Tom Swift. Swindlers and
thieves are always on the alert for a chance to rob a jewelry store, and
they work many games."

"I didn't notice any particular man looking in here," said Tom, who
still held the diamond brooch in his hand.

"Well I did," went on the jeweler. "I happened to glance out of the
window when you were looking at the pins, and I saw his eyes staring in
here in a suspicious manner. He may have a confederate with him, and,
when you're gone, one may come in, and pretend to want to look at some
diamonds. Then, when I'm showing him some, the other man will enter,
engage my attention, and the first man will slip out with a diamond ring
or pin. It's often done."

"You seem to have it all worked out, Mr. Track," observed the lad, with
a smile. "How do you know but what I'm in with a gang of thieves, and
that I'm only pretending to want to buy a diamond pin?"

"Oh, I guess I haven't known you, Tom Swift, ever since you were
big enough to toddle, not to be sure about what you're up to. But I
certainly didn't like the looks of that man. However, let's forget about
him. He seems to have gone down the street, and, after all, perhaps I
was mistaken. Just wait until I show you a few more styles before you
decide. The young lady may like one of these," and the jeweler went to
another showcase and took out some more trays of brooches.

"What makes you think she's a young lady, Mr