I exchanged weapons with Miriam, and pointed to the spot on the wall. She backed up against the other side of the tunnel and took a knee, aiming the light to give me a nice big circle for a target. I made a gesture with my gun, and Miriam nodded. She got the short code, no fuss, no problem, and slipped the H&K safety off and the selector to triple burst, just like I’d showed her. I set the other MP5 against the cavern wall. The sledgehammer felt good in my hands. The wooden handle was old and I figured it had been impregnated with the sweat of working people like Daniel, their callused hands smoothing down the oak until there it was now, in my fists, tight-grained, dark with use, ready.

I swung the steel head in a long horizontal arc. The entire motion was a force multiplier, transferring the mechanical work into kinetic energy gathering in the steel head. The steel hit stone with a thick thwack that echoed in the confined tunnel. I’d hit the sweet spot, deep and hard. I reset immediately and swung again. Same thing. Steel cracked against the limestone wall. The seventh strike penetrated. The hammer head got stuck in and I had to pull it out with a violent tug. I made two more hits in quick succession, and we had a hole.

Seven big hits, two secondary. I’d made some noise. So it was a gamble going through.

I tossed the sledgehammer aside and picked up the H&K. When I looked up, Miriam was already in, a fast mover. The hole was a good size for her, not so good for me. I lost sight of her, which wasn’t a good thing. But then she was looking back at me. I got through the narrow opening and she shone her light around.

We had passed through a thick membrane of limestone, into a large space shaped like an egg sliced lengthwise. The other half of the egg was blocked off by a man-made wall. The cave we were in had higher ceilings than the tunnel we’d taken from the Vaugeois cavern. Mineral deposits rose up from the floor in spikes, other spiky stone formations hung from the ceiling. This was a natural cave, not excavated by hand. But the wall wasn’t natural, it was made of cinder blocks, and around fifteen feet high, by twenty feet wide.

I whispered, “We’ll have to put a hole in that, but it’ll attract attention on the other side.”

Miriam whispered back, “Can you break through in one shot?”

“Not one shot, more like five. Problem is, that wall was built as a sound barrier.”

“How’s that?”