“Is anyone bleeding?” Everyone shook their head. “Good, but I’d also suggest that if someone needs to go to the toilet, please do so on dry ground. Though our suits are designed to absorb waste, I notice a few abrasions appearing in the material; so . . .” Alex didn’t need to say anymore. Just the thought of the worms invading where and when a person was most vulnerable made everyone decide to try and squeeze out any last drops of urine before they potentially had to re-enter the stream. They only separated as far as was needed for modesty and Aimee, being the last one in the line, thought she heard something break the water’s surface away in the dark, something that had to be much larger than any invertebrate worm they had encountered.

Within five minutes they were ready to go. The small group walked in silence to the choke, with the only sounds the scrunching squeak of the black sand beneath their feet. Alex and Monica took the lead. As Alex walked along the narrow beach beside her he looked down at his legs which were covered in a black shiny mineral. “What is this stuff?” he asked her. “It’s sticking like glue.”

Monica wiped her finger down her leg and brought it up to roll some between her thumb and forefinger. “Probably magnetite; it’s a mineral that’s crystallised from basaltic magma. Usually where you see it like this it has weathered out of the basalt and has accumulated as sand on beaches. It also indicates prehistoric volcanic activity; never expected it down here though—that and a lot of things. By the way, it’s not sticky, but slightly magnetic—keep it away from your electronics and weapons otherwise it will cause them to lock up.”

“Good point. Gentlemen, pack your weapons and keep them away from the sand—it’s magnetic particles.” Tank and Takeda nodded and pushed their rifles over their shoulders into their packs.

The team moved slowly in the darkness and after twenty minutes they came to the choke. It blocked the cave and the stream ended in a slight belly as the water had to slow down in front of the huge pile of tumbled stones. On the surface slight whirlpools could be seen where the water was being sucked through the choke via small crevices. Monica waded in along the edge of the cliff wall and leaped up onto the choke, scrambling to the top. She scurried back and forth for a while then rejoined the team. “Good news; it’s an apex choke—smaller at the top. At the centre, the debris is smaller.”

“Can we blast our way through? We can set our rifles to produce a broader air projectile that could provide a non-explosive hammer effect.” Monica thought about it for a while, and then turned back to Alex.