“Do you really think so, Dave?”

“Not think, but know so!” declared Kilgore, with emphasis.  “I know these Carters, root and branch.  They have now struck our trail, and they’ll stick to it like bloodhounds till they run us down—­unless we get them!  It must be done, I say, and done promptly.”

“Put them down and out?”

“Exactly.  It’s them—­or us!”

“And why do you think, all of a sudden, Dave, that Nick Carter is so hot on our heels?”

“I’ll tell you why, Spotty.”

And Mr. David Kilgore, chief of the notorious diamond gang bearing his name, and one of the keenest and coolest criminals in or out of prison walls, removed his pipe from his mouth and his heels from the edge of the table, and drew forward in his chair to explain.

It was a curious place, that in which the speakers of the above were seated, in the bright glare of an electric light.

It was inclosed with four solid stone walls, with not a window or aperture through which a ray of light could be detected from outside.

Yet in one of the walls was a low, narrow door, also of stone, and so cleverly constructed and fitted that, when swung into place in the wall, it was comparatively beyond the detection of anybody ignorant of its existence.  This door then stood open, but the aperture through the wall was heavily curtained.

Three of these walls formed the original foundation of an old and extensive suburban mansion, the location, ownership and present use of which will presently appear.  The fourth wall, that with the door, was of more recent construction, and was built squarely across the original cellar of the house.  It had been made to mask this secret subterranean chamber in which the Kilgore gang was then gathered.

The place was commodious, and contained some noteworthy objects.  In one corner was a powerful hydraulic press.  Near by was a splendid electrical furnace, capable of generating an extraordinary degree of heat.  Against the adjoining wall were several barrels of sulphur, of which only one was unheaded.  Near by was a large box of anthracite coal, black and glistening in the rays of the arc light.

Parallel with the opposite wall was a workbench, laden with curious retorts, crucibles, test tubes, metal molds, and no end of tools, all of which plainly suggested the work of one versed both in chemistry and some mechanical art.

In the middle of the room was a square deal table, at which Kilgore was seated, with Matt Stall and Spotty Dalton, the original three of the Kilgore gang.

Two other persons were present, however, and they were engaged in examining some work on the bench mentioned.

One of them was a tall, angular Frenchman, about sixty years of age, named Jean Pylotte.  He had a slender figure, somewhat bowed; but his head was massive, in which his gleaming, gray eyes were deeply sunk, like those of a tireless student and hard worker.