Tunnels 01, Tunnels

Below were two rows of angular lettering. The symbols were unfamiliar and made no sense to him at all.
    "What's this? Some kind of marker or milestone?" Will looked up at his brother, who shrugged his shoulders unhelpfully.

    * * * * *

    Several hours later, the going had become slow and laborious. They came to fork after fork in the tunnel, and Will had to consult the map even more frequently. They'd already taken one wrong turn; luckily they hadn't gone too far before Will realized his mistake and they had painstakingly retraced their steps and found their way back to the correct path again. Once there, they had flopped onto the sandy floor, stopping just long enough to catch their breath. Although he was trying to fight it, Will felt unusually tired, as if he were running on empty. And when they resumed their journey, he felt weaker than ever.
    Whatever state he was in, though, Will didn't want Cal to suspect anything was wrong. He knew they must keep going; they must keep ahead of the Styx; they had to get out. He turned to his brother beside him.
    "So what does Tam do in this EternalCity?" he said, breathing heavily. "He was very cagey when I asked him about it."
    "He searches for coins and stuff like that, gold and silver," Cal said, then added, "most of it from graves."
    "Graves?"
    Cal nodded. "In the burial grounds."
    "So people really lived there?"
    "A long time ago. He thinks that several races occupied it, one after the other, each building on top of the last. He says there are fortunes just waiting to be found."
    "But who were these people?"
    "Tam told me the Bruteans were the first, centuries ago. I think he said they were Trojans. They constructed it as a stronghold or something, while the Topsoil London was built above.:
    "So the two cities were connected?"
    Cal's mask nodded ponderously. "In the beginning. Later the entrances were blocked up, and the stones marking them were lost... The EternalCity was just forgotten ," he said, puffing noisily through the air filter. He looked nervously back up the tunnel, as if he'd heard something.
    Will immediately followed his glance, but all he could see was the shadowy form of Bartleby as he loped impatiently from one side of the tunnel to the other. It was clear that he wanted to go faster than the two boys, and from time to time he would speed past them but then stop to sniff at a crevice or the ground up ahead, often becoming visibly agitated and letting out a low whine.
    "At least the Styx will never find us in this place," Will said confidently.
    "Don't count on it. They'll be following us, all right," Cal said. "And then there's still the Division in front of us."
    "The what? "
    "The Styx Division. They're sort of a... well... border guard," Cal said, searching for the right words. "They patrol the old city."
    "What for? I thought it was empty."
    "There's talk that they're rebuilding whole areas and patching up the cavern walls. It's said that the whole Colony might be moved there, and there's rumors of work parties of condemned prisoners, toiling like slaves. It's only rumors, though -- no one knows for sure."
    "Tam never mentioned anything about more Styx," Will didn't attempt to hide the alarm in his voice. "Bloody brilliant," he said angrily, kicking a rock in his path.
    "Well, maybe he didn't think it would be a problem. We didn't exactly leave the Colony quietly, did we? Don't get too worried, though; it's a huge area to cover and there'll only be a handful of patrols."
    "Oh, great! That's a real comfort!" Will replied as he imagined what might be in store for them ahead.
    They wandered on for several hours, eventually scrabbling down a steep incline, their feet slipping and sliding in the red sand until they finally reached a level area. Will knew that if he'd been reading the map correctly they should be approaching the end of the Labyrinth. But the tunnel narrowed before them and appeared to end in a blind alley.
    Fearing the worst, Will raced ahead, stooping as the roof lowered. To his relief, he found that there was a small passage to one side. He waited until Cal caught up, and they looked apprehensively at each other as Bartleby sniffed the air. Will hesitated, looking repeatedly from Tam's map to the opening and back again. Then he met Cal's eyes and smiled broadly as he edged into the narrow passageway. It was bathed in a subdued green light.
    "Careful," Cal warned.
    But Will was already at the corner. He became aware of a familiar sound: