Dropping on his knees, he carefully examined the floor and the iron-shod threshold of the door, probing the narrow slit with his knife. This done, he turned his attention to the walk and the crown of the arch next to the woodwork, tapping the stone with the blade of his knife with the greatest caution.
The others looked on with interest not unmingled with curiosity and awe. At length, apparently satisfied with the examination, Mr. McKay rose.
"I want you to bore a hole here," said he to Andy, pointing out a place in the door barely two inches from the floor.
Andy, armed with a ratchet-brace, began his task, and the subdued silence of the underground passage was broken only by the rattle of the pawl and the sharp burr of the bit as it wormed its way steadily through the stout oaken plank.
"It's hot work," exclaimed Andy, who in order to use the brace in that most inconvenient place was obliged to lie full length on the floor.
"I know, but keep it up," replied Mr. McKay, who, grasping a crowbar, was standing astride his son's feet.
"Stand a bit farther back," he continued, addressing Ellerton and Terence.
The two lads instantly obeyed, though they wondered at Mr. McKay's alert and expectant attitude.
Suddenly, like the tongue of an enormous serpent, a double-pronged barb of steel flashed dully in the candle-light, passing completely across the passage and about three feet above and over Andy's prostrate body.
In an instant Mr. McKay's powerful arm brought the crowbar upward in a resistless sweep, and with one blow severed the dreadful device of death.