Tunnels 02, Deeper

down the main tunnel when Cal stopped and pointed at a side passage. True to form, he had wandered ahead by himself, and now did not say anything as he continued to point.
    "Is the midget trying to tell us something?" Chester asked Will sarcastically as they approached the resentful boy. Will stepped closer, until his face was inches from Cal's.
    "For goodness' sake, grow up, will you? We're all in this together."
    "A sign," Cal merely said.
    "From heaven?" Chester asked.
    Unspeaking, Cal moved aside to allow them to see a wooden post that rose a few feet from the ground. It was ebony-black, with the surface cracked as if it had been badly charred, and at the top it had a curved arrow pointing into the passage. They hadn't spotted it on the way down because it was tucked just inside the mouth of the passage.
    "I reckon this could be a good way to get through to the Great Plain," Cal told Will, studiously avoiding Chester's belligerent glare.
    "But why would we want to go there?" Will asked him. "What's so special about it?"
    "It's probably where your dad went next," Cal replied.
    "Then we follow it," Will said, and turned away from his brother, entering the passage without a further word.

    * * * * *

    Their journey through the passage was relatively easy -- it was quite sizable, and its floor level, but the heat grew stronger with every step. Following Chester's and Cal's example, Will had removed his jacket, but he still felt the sweat soaking his back under his rucksack.
    "We are going in the right direction, aren't we?" he said to Cal, who for once was not straying ahead of them.
    "I hope so, don't you?" the boy replied insolently, then spat on the ground.
    The change was immediate. There was a flash of illumination, far brighter than the glow issuing from the lanterns all three boys had hooked on their shirt pockets. It was as if all the faces of the rocks, and even the very ground itself, were radiating a clean yellow light. And it wasn't just limited to where they stood, but surging in pulses along the passage in both directions and illuminating everything as surely as if a switch had been flicked on, lighting the way for them.
    They were stunned.
    "I don't like this, Will," Chester gibbered.
    Will pulled his jacket from where it was draped over the top of his rucksack and rummaged in it for his gloves.
    "What are you doing?" Cal asked.
    "Just a hunch," Will replied, stooping to pick up a brightly glowing rock the size of a golf ball. He closed his gloved hand over it, the creamy efflorescence shining through the gaps between his fingers. Then, balancing the rock on his open palm, he examined it carefully.
    "Look at this," he said. "See that it's covered with a growth of some sort, like lichen?" Then he spat on it.
    "Will?" Chester exclaimed.
    The rock shone even more brightly. Will's mind was working overtime. "It feels warm. So moisture activates whatever this organism is -- possibly bacteria -- and it gives off light. Except for the stuff you find in some oceans, I've never heard of anything quite like this." He spat again, but this time on the wall of the passage.
    Sure enough, where spots of his saliva had landed, the wall glowed that much more fiercely, as if luminous paint had been flicked at it.
    "C'mon already, Will!" Chester said urgently, his voice low with fear. "It could be dangerous!"
    Will ignored him. "You can see what water does to it. It's like a seed that's dormant... until it gets wet." He turned to the other two boys. "Better not get any on your skin -- wouldn't like to think what it might do to it. Might suck up all the moisture..."
    "Thank you, Professor Smarty-Pants. Now let's get out of here ASAP, shall we?" Chester said, exasperated.
    "Yep, I'm done," Will agreed, tossing the rock aside.

    * * * * *

    The rest of the journey was uneventful, and it was many hours of monotonous trudging before they left the passage and came out into what at first Will took to be another cavern. But as they moved forward, it soon became apparent that the space was something altogether different from any of those they'd been in before.
    "Hold up, Will! I think I can see lights," Cal said.
    "Where?" Chester asked.
    "There... and more over there. See them?"
    Both Will and Chester peered into the seemingly unbroken blackness.
    To catch sight of them, they had to look just off center -- attempting to view the lights directly blotted the dimly blinking specks from view.
    In silence, they turned their heads