Tunnels 04, Closer

looking at some sort of inverted sea. He also noticed where the waves were lapping over into funnel-type structures set into the roof of the cavern. Inside each of these something was spinning around. "So those are the fans?" he guessed.
    Drake nodded. "You hear that low humming? Those things up there are like giant extractor fans. This is one of several locations where the stale air is drawn out of the South Cavern and vented to the surface via disguised flues."
    "So we get all this smoke Topsoil, instead?" That's not right," Chester decided, frowning. "I thought Eddie was dead against pollution? Remember all that stuff he said to me?"
    "Forget it -- he was playing mind games with you. Never trust anything a White Neck tells you," Drake replied. With a " shh ," he held his hand up. "Like clockwork -- the changeover is precisely on the hour," he whispered. "Stay down. Make sure he doesn't eyeball you."
    As Chester remained pressed against the wall behind Drake, he caught a glimpse of a squat man trundling up the track. The man couldn't see them where they were hiding as he made for the flight of steps, then began to ascend to the control room.
    "Do we go now?" Chester asked.
    "Not quite yet," Drake said.
    Then Chester saw that a different man was coming down the steps. He lingered at the bottom to light a long-stemmed pipe before setting off.
    "Right -- the next shift has just taken over, so we're good to go," Drake announced. With Chester close behind, he hurried over to the steps and then mounted them two at a time, his tranquilizer pistol ready in his hand. He stopped as they reached the door at the top. "The control room is always manned. That Colonist's in here, and there may be more, so keep your eyes peeled."
    The old iron door was unlocked, and Drake gently pushed it open so they could slip inside. Chester found that they were in a long gallery, with a row of windows in wooden frames down one side. It was similar in appearance to a train carriage from a bygone era, although it was wider and longer than any Topsoil carriage. And to the other side, the wall was formed by an incredible latticework of archaic pipes, all of highly-buffed brass and secured to panels of dark oak. Not only were there numerous levers and valves on these pipes, but also dials and gauges that clicked and twitched in unison.
    The noise Chester had heard below was far louder up here -- a regular and very low thump, which made his skull reverberate. The impression that he was actually inside some gargantuan beast recalled to him his favorite story from the Bible, Jonah and the Whale . However this was far different -- it was as if he'd found his way not into the belly of the beast, but its lungs.
    Drake took it slowly as he crept further into the gallery.
    Then, tucked away in an alcove amongst the pipework, they came across the Colonist.
    With a shout, the stocky man leapt up from a table, a pack of playing cards flying from his hands and into the air. Dressed in dark gray overalls, he had bristly white hair and a red scarf tied around his neck. He shouted again, grabbing a ludicrously oversized spanner from the side of the table.
    "Sorry," Drake said, then fired his pistol, dropping the man where he stood with a tranquilizer dart. Out cold, the Colonist fell forward onto the table, which splintered under his not inconsiderable weight. Drake rolled him over to make sure than he hadn't been injured in the fall. The dart was still stuck in his massive chest.
    "Colonists," Chester murmured, his lip curling in disgust. "I really hoped I'd never see one of those head cases again in my life."
    "This man isn't your enemy," Drake said, noticing how the boy's hands had tightened around his rifle. "He's just doing his job."
    "Yeah -- just like that creep in the Hold," Chester scowled. "He was called the Second Officer -- and he was just doing his job too."
    Taking a folded piece of paper from inside his jacket, Drake shook it open and passed it to Chester, who was still staring at the unconscious man. "This is important. I need you to concentrate," Drake ordered the boy. "Look at this drawing."
    "What about it?" Chester asked, as he relaxed his grip on his rifle and turned his attention to the line drawing. It showed a panel with five large gauges on it, and a whole series of pipes below it.
    "This measures the pressure of the air being pumped into the cavern." Drake swung to the wall of pipes. "We'll start from either end, and work our way into