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. His companion at the bench just then was Sanetta Cervera, the Spanish dancer--the murderess of Mary Barton--the vicious dare-devil who had served Nick Carter one of her evil tricks that very evening. Cervera had arrived at the diamond plant less than an hour before, and had hurriedly told her confederates the whole story of her crime and her adventure with Nick. Crime was too common with these outlaws, however, and loyalty to one another too natural, for Kilgore to censure his only female confederate very severely. Yet as Kilgore now proceeded to explain, her crime had rendered their situation decidedly more alarming. "I'll tell you why these Carters are now to be seriously feared," said he, nodding grimly at his hearers. "This last move of Cervera has hurt us severely." "In what way?" demanded Spotty Dalton, the pock-marked chap who had relieved Venner's partner of the Hafferman diamonds about two weeks before. "I don't see just how, Dave." "No more do I," put in Matt Stall. "You'll see," replied Kilgore, "when I run over a few facts which led to our being here, and at work on our present game."