Tunnels 02, Deeper

He pulled back slightly, vexed. Then he leaned forward again, forcing Cal's jaw farther down to check that his airway wasn't blocked by an obstruction, and once again cocked his head to one side to listen. Blowing through his lips, Chester sat back on his haunches and placed his hand on the boy's chest.
    "Will! I don't think he's breathing!"
    Will grabbed his brother's limp arm and shook him.
    "Cal! Cal! Come on! Wake up!" he cried.
    He placed two fingers on the boy's neck, feeling for the artery and frantically trying to find a pulse.
    "Here... No... Where is it?... Nothing... WHERE IS IT?" he yelled. "Am I doing this right?" He looked at Chester, his eyes wide with the wrenching, screaming awareness that he couldn't find a heartbeat.
    That his brother was dead.
    At that very moment, the clicks were replaced by another sound. A soft popping similar to that of champagne corks going off, but gentler, as if heard through a wall.
    A streaming, fluxing whiteness instantly filled the air. The deluge engulfed the boys, catching in the beams of their lights and clogging the space. These particles, like a million tiny petals, spewed forth in torrents. They could have been coming from the tubes, but it was so dense it was impossible to tell.
    "No!" Will shrieked.
    With a hand clapped over his nose and mouth, he began to heave his brother by his arm, trying to drag him toward the entrance of the cavern. But Will found he couldn't draw breath; the particles were like sand, blocking his mouth and nostrils.
    He arched his back and swallowed a little air, enough for him to shout a few words at Chester. "Get him out!" he cried over the incessant popping.
    Chester didn't need to be told, but was floundering under the onslaught, blinking and shielding his eyes as the dry, snow-like material continued to spurt forth. The air was so thick and impenetrable that, as he waved at Will, his arm left swirling eddies behind it.
    Will slipped and fell to the ground, coughing and choking. "Can't breathe," he wheezed with what little air he had left in his lungs. Lying on his side, he struggled to fill them again, cursing inside as he thought of the gas masks he and Cal had used in the EternalCity. They'd dumped them, figuring they would be of no further use. They'd been wrong.
    With his hand held over his face, Will stayed on his side, panting, unable to do anything. Through the deluge he saw Chester hauling Cal along, the boy's body leaving tracks behind it in the whiteness.
    Will forced himself to crawl, his lungs aching from lack of oxygen, his head spinning. He couldn't think about his brother; he knew he was going to succumb if he didn't get out of the cavern. His throat and nostrils were blocked as if he'd been buried in flour. With a supreme effort he staggered to his feet and managed a few steps. Chester, his back to Will, was still pulling and heaving Cal's lifeless body.
    Will launched himself forward, propelling himself only a couple of paces before collapsing to the ground again. It was enough. He was away from the worst of the swirling maelstrom of whiteness and able to suck in some clean air.
    He continued at a slow crawl but hadn't gone very far when he doubled up and coughed so much he was sick, uncontrollably so. To his horror, his vomit was awash with the minute pale particles and small slugs of blood. With the single thought of survival in his mind, he forced himself down the passageway on his hands and knees, pulling himself blindly through the narrow stretch, and didn't stop until he'd reached the letterbox opening.
    He heaved himself back out onto the Great Plain and lay coughing and spluttering and throwing up a mottled fluid. But his ordeal wasn't over yet. Where the white specks had stuck to the exposed skin of his neck and face, they began to irritate it, the irritation very quickly transforming into the most excruciating burning sensation. He tried to scratch off the particles, but this just seemed to make things worse: As the white specks came away, they took the skin with them. Soon blood was smeared all over his fingers.
    Not knowing what else to do, he grabbed handfuls of dirt and scrubbed furiously at his face and neck. This seemed to do the trick, the intolerable itching and pain easing a little. But his eyes were still on fire, and it took him some minutes to wipe them clean using the inside of his shirtsleeve.
    Then Chester appeared. He scrambled up through the opening, staggering around blindly. As he fell on