Matt reached out and touched it. It was quite solid. “You said it was soft?”

Andy reached out and stuck a finger in. “It was softer than this.” He turned and looked over their shoulders. “Can we…?”

Tania spun. “Turn that light over here.”

One of the halogen stands was swung around and they were lit up like stage actors. Andy backed up a step.

“Notice something strange, Frank?”

The older man folded his arms. “Yup; most of the surrounding strata down this far is Cambrian-age bedrock, some shale, and a little limestone for good measure. Most that is, except that section right there.” Frank pointed with a thumb to the ten-foot-wide area Andy had just been examining up close.

“Bingo. It’s hardening up now, but still not rock.” He held a hand out to Matt. “Stand back, Prof; real men at work.” He grabbed a medium-sized shovel and gently stuck it into the wall. He pushed and then levered free a bucket-sized clod, and used the shovel end to gently mash the soil flat. “Still soft, and not even rock fragments; it’s like there was a tunnel here that was filled in.” He looked back to the wall. “But nothing I know of could do it that completely without leaving a trace of the excavation work.” He turned to Tania. “Could you guys? The military, I mean.”

Her mouth turned down and she slowly shook her head. “We’ve got equipment and techniques that are powerful, fast, and adaptive, but not pretty. There’d be traces of any work done by a team like ours.”

“That’s what I thought.” Andy turned back to the wall. “Frank, give me a hand – let’s see where this rabbit hole leads.”

Matt watched as together the two men gently shoveled dirt from the section. Tania had her soldiers clear away the debris, piling it further along the cave. The piles grew as the hole became deeper; and after about fifteen minutes, the pair had dug about five feet into the wall. The going had been fairly easy due to the softness, but still, working in the thick suits must be hot and fatiguing.

Andy stopped. Frank was already leaning on his shovel, slightly bent over.

“Hot.” He wiped at his forehead, and then growled at not being able to reach the damp skin behind the faceplate. Matt could see that Frank’s face was once again very red and streaming with perspiration.

Tania obviously saw the same. “Shift change.” She pointed to the two young soldiers. “Jackson, Morris, take over, and easy as you go.” She turned to Andy but spoke to her men. “Mr Bennet here will supervise.”

Andy handed over his shovel, and the two men set to deepening the tunnel.

After a further twenty minutes, the lights behind them had to be re-angled to illuminate the hole’s depth. They had dug in close to twenty feet, the soldiers having made much better headway than the geologists.

Jackson dug in hard, and a slab of earth fell away. He called over his shoulder. “Got something.” He stepped aside.