Tunnels 03, Freefall

"Stupid, stupid, stupid!"
    "Will, we did look for passages on the right, and we didn't find any, did we? Just calm down," Dr. Burrows urged him.
    "No, I won't! What if they were hurt in the explosion? Chester might need my help."
    "I'm sure he's fine. The renegade woman will look after him, and that girl with all the explosives -- she was no shrinking violet. Bet she knows the ropes down here," Dr. Burrows said.
    "Her name is Elliott," Will fumed, throwing his father a look of irritation. "And she's just as lost down in this place as we are. And at this rate we're going to get ourselves doubly lost."
    "I think not," his father countered.
    Will was about to vent more of his frustration, when he stopped himself. "Why do you say that?"
    "Because if you had been paying attention for the last couple of miles, you would have observed those." Dr. Burrows shone his luminescent orb on an area higher up the wall. Although the paint was faded and had peeled away in places, a red triangle was immediately above where Will was standing, one of its tips pointing in the direction they had been going. "There were just a few at the beginning, but now they're running at about five hundred yard intervals."
    Will was instantly curious. "Do you think the crew from the submarine left them?"
    "Possibly," Dr. Burrows said. "But we're going to find out for ourselves what's at the end of the trail."
    "No way... I've got to go back for the others," Will insisted, but his words had lost some of their conviction. His eyes widened as his insatiable thirst for discovery took hold. "Though... I suppose it wouldn't do any harm to follow the signs for a bit."
    Without further ado he pushed on into the narrow chasm.
    "That's my boy," Dr. Burrows said under his breath.
    They struggled through the claustrophobic corridor for several more kilometers. All of a sudden the reports of their footfalls seemed to have a different quality to them, the echoes indicating that they were coming to a much larger space.
    "Light -- more light," Dr. Burrows ordered, as they stepped from the corridor and found to their surprise that they were on some sort of level platform. Will turned his lantern up several clicks. "This is concrete!" Dr. Burrows said, grinding his heel into the surface. Then he dropped onto one knee to examine it more closely, all the time twittering to himself. "Concrete... probably cold-poured."
    But Will was so excited he wasn't listening. "Look! There's a line!" he shouted as he directed his lantern before them. A thick white line was revealed, running straight across the way ahead. And just beyond the line, something glinted darkly, giving the impression of movement.
    Father and son immediately advanced towards it, trying to make out what was there.
    "Careful," Dr. Burrows warned Will.
    "It's okay, it's just water," Will said as they came to the line and stopped. The line marked the edge of the platform, and as they both peered down, they could see there was a drop of several meters to where the expanse of water began. Although it appeared to be quite deep, it was clear enough that rocks were visible at the bottom.
    "Yes, some sort of subterranean pool," Dr. Burrows confirmed. "I wonder what else is here."
    Will immediately began to shine his beam out over the gently lapping surface. As he did this, shifting crescents were thrown against the far wall to the left of the cavern. They both squinted at it through the murky gloom.
    "This place is enormous," Will said unnecessarily. He switched his lantern to its full setting so he could see further along the cavern wall.
    "It is," Dr. Burrows murmured, although he still seemed to be more interested in the platform underfoot, turning his attention to it again. "What is a damned great slab of concrete doing down here? What the devil's it for?" he posed to himself as he scraped his boot slowly across its surface.
    "I'm going to check up here," Will said, as he followed the white line where it ran to the left. Finding that the platform terminated at the cavern wall, he shouted, "Nothing doing -- dead end!" He went back to where his father was standing but didn't stop, passing behind him. He thought he'd reached the other end of the platform as he came to a large pile of rubble, but as he climbed over it he found the concrete platform extended far into the darkness, its level surface only interrupted by the odd crack and by pieces of rock strewn across it.
    "There's more here!" he reported to his father,