and an oil cooker completed the domestic arrangements. But what attracted his attention most was the passage-like aperture which opened from the innermost comer of the rocky chamber.
"Where does that lead to?" he asked quickly.
Inspector Renshaw looked at him for an instant without speaking, apparently undecided how far to take him into his confidence.
"I will show you something that will surprize you," he said at length. "Follow me."
Unhooking a portable electric lamp from a peg driven into a crevice in the rock wall, he switched it on and led the way through the narrow aperture. With growing excitement Hugh saw that the tunnel, unlike the cavern they had just quitted, had walls comparatively smooth, and in places he could even distinguish the marks of the tools with which they had been hewn.
"This passage has been made for a definite purpose," he exclaimed, his voice sending weird echoes booming hollowly out of the wall of blackness ahead.
"Speak lower," warned his guide. "This place carries sound like a huge speaking-tube, and it would spoil my plans if its existence became known. Yes," he went on, in answer to Hugh's question, "this is nothing more nor less than an abandoned mine, so ancient that its very existence has been forgotten."
"Mine?" repeated Hugh, with a dubious shake of his head. "What sort of mineral could have been dug out of here?"
Renshaw shrugged.
"I'm afraid I'm not sufficiently expert in mineralogy, sir, to answer that question. But there are plenty of old workings in the Mendip Hills—some thirty miles away in a northeasterly direction—where they used to get lead-ore and calamine, and some of them are being operated at the present time. I should say that this has been a mine of that description. You'll notice that the galleries do not run in a straight line, but wind about as they followed the veins of ore. There are about a couple of dozen side passages. There is one of them"
He swung the beam of his lamp to the left, and Hugh caught a glimpse of the mouth of a tunnel that was even narrower and lower than the one they were traversing.
"Where does it lead to?" he asked.
"I haven't explored that particular one," Renshaw answered carelessly. "I took a look down a few of them, but they all ended suddenly, some in clayey earth, others in a kind of black rock. I suppose they were abandoned when the veins petered out."
"Where does this particular tunnel lead?" Hugh was conscious of a vague feeling of uneasiness as he put the question. "We must have travelled a fairly good distance—though the air is fresh enough. Where are we?"
"You'll see in a few minutes," the detective parried, at the same time half turning and throwing a smiling glance at Hugh.
Ever since they had entered the tunnel Hugh had noticed that the ground had been sloping gently upward. Now, however, the tunnel took a steeper incline. Presently Renshaw paused and pointed to a roughly drawn arrow, chalked on the rock at the entrance to another side passage.
"I put that there so that I shouldn't miss my way," he explained. "We turn off here."
A dozen paces in this new direction, and Hugh was conscious of a strong current of air blowing in his face. The
