The rattle was not a sudden explosion, but it was far more lethal.

It began as a low, dry clicking beneath the damp floorboards of the *Ember*—a rhythmic, metallic *clack-clack-clack* that vibrated through the seasoned oak hull. The steam engine was dead, its furnace damped to a smoldering bed of gray ash, but the massive copper steam lines were contracting too fast in the sub-zero air of the Ice-Needle Tunnels. As the metal shrank, a loose mounting bolt in the primary exhaust line had sheared its threads. Now, the heavy copper pipe was vibrating against the iron engine frame like a trapped bird beating its wings against a cage.

To any surface dweller, the sound would have been negligible, easily drowned out by the wind. But deep inside the Screaming Glaciers, where the ice had been compressed by centuries of tectonic weight until it was as dense and brittle as tempered glass, the rattle was a death sentence.

Cormac Reed stood motionless at the tiller, his left hand clamped onto the frozen wood. His right arm hung stiffly at his side, wrapped in a thick, mud-encrusted bandage that had frozen into a rigid, stone-like cast. He didn't need to look up to know what was happening. His heightened acoustic sensitivity—a sense carved out of years spent in the absolute dark of subterranean rivers—registered the shift in the cavern’s atmosphere before anyone else.

The low-frequency vibration of the pipe was traveling up the basalt walls, resonating directly into the ceiling.

Above them, the thousands of needle-sharp ice stalactites did not fall. They began to sing.

It was a high, glassy hum that set the teeth on edge, a sound like a wet finger tracing the rim of a thousand crystal goblets. The air in the narrow tunnel grew instantly heavier, vibrating with a physical pressure that squeezed Cormac’s scarred lung. He could feel the low-frequency hum rattling the bones of his chest.

Beside him, Toby Miller was crouching near the main mast, his pale face illuminated only by the faint, blue glow of the Guild’s mapping device. The young cartographer’s brass-rimmed spectacles were heavily fogged with frost-rime, but his eyes were wide with terror. He looked up at the ceiling, his hands shaking so violently that he had to press his elbows against his ribs to steady them.

Toby raised a single, wool-wrapped finger, pointing toward the dark canopy of ice.

In the dim, blue light, a fine, glittering powder was beginning to drift down from the tips of the daggers. The Hardened Glacier Ice was starting to fracture at its roots. The acoustic resonance was reaching its critical threshold.

Cormac caught Toby’s eye. He didn't dare speak; even a whispered word could be the final grain of sand that broke the ice. Instead, Cormac made a flat, slicing motion with his left hand across his throat—*absolute silence*.

He gestured to Garrick Vance, who was standing by the engine hatch, his broad shoulders tense, his face blackened with grease and white with frost. Cormac pointed to the tiller, then to his own useless right hand, and finally toward the floorboards.

*Take the rudder. I'm going under.*

Garrick nodded, his expression grim. He slid onto the bench, his massive, scarred hands taking the tiller with a slow, deliberate grip that didn't make a single sound. He braced his boots against the wet deck plates, ready to guide the drifting longboat through the narrow basalt channel on manual power alone.

Cormac knelt. The movement sent a sharp, sickening spike of pain through his bruised ribs—a reminder of the tiller’s violent kickback during the rapids run—but he didn't allow his face to change. He slipped his left hand into his heavy caribou-skin coat and pulled out Declan's Coal Hand-Warmer.

The small brass pocket furnace was warm to the touch, its internal chamber filled with slow-burning, crushed anthracite dust that radiated a faint, steady heat. It was their only portable source of localized warmth, a tiny beacon of fire in a world that wanted to freeze them solid. He tucked the brass warmer into the palm of his glove, feeling the heat begin to seep through the leather, before sliding his body down into the narrow hatch that led beneath the deck plates.

The space beneath the floorboards was a dark, claustrophobic tomb. It was barely two feet high, choked with the smell of stagnant bilge water, sulfurous soot, and the bitter, metallic tang of cold copper.

As Cormac crawled forward on his belly, the freezing bilge water soaked through his caribou-skin suit within seconds. The water was near-freezing, a black, sluggish soup that clung to his skin like liquid ice. The cold-shock was immediate, a physical blow that threatened to force a gasp from his throat. He clamped his teeth together, utilizing the deep-lung expansion breathing Alistair Thorne had taught him, forcing his heart rate to slow, his metabolism to drop.

*Control the breath. Let the cold in, but do not let it take the center.*

He dragged his body forward, his useless right arm scraping against the iron ribs of the hull. Every scrape sounded like a mountain falling in his ears. He reached the primary exhaust line, his eyes adjusting to the absolute blackness under the deck.

*Clack-clack-clack.*

The copper steam line was vibrating violently. The mounting bracket had snapped its primary bolt, and the heavy pipe was striking the iron hull plate with every movement of the water. The vibration was traveling directly into the keel, transforming the entire thirty-ton boat into a massive acoustic tuning fork.

Cormac reached out with his left hand, his fingers searching for the sheared bolt. He found it—a jagged piece of iron protruding from the bracket. He reached into his tool roll, his numb fingers searching for his small copper spanner wrench.

His fingers were unresponsive. The freezing bilge water had stripped them of all sensation, leaving his hand like a heavy, wooden block. He tried to grip the wrench, but his fingers simply wouldn't close. The metal tool slipped from his hand, falling into the dark bilge water with a soft, wet *plop*.

Cormac froze.

Above him, the screaming of the glaciers grew louder, the pitch shifting from a hum to a high, metallic shriek. The ice needles were beginning to crack. A small, sharp shard of ice fell from the ceiling, striking the deck plate directly above his head with a sharp *thud*.

He had seconds before the entire cavern collapsed.

He couldn't search for the wrench in the dark, freezing water. His fingers were dead. He needed sensation, and he needed it now.

Cormac pulled Declan's Coal Hand-Warmer from his coat pocket and pressed his bare, numb fingers directly against the hot brass casing.

The transition was agonizing. The intense, localized heat of the coal dust hit his frozen nerves like a cluster of red-hot needles. It was the screaming pain of the "dead nerves" returning to life—a burning, white-hot torture that made his vision go dark at the edges. He wanted to scream, to tear his hand away, but he held his breath, forcing his fingers to stay clamped around the hot brass until he felt the dull, throbbing return of his motor control.

His hand was shaking, but he could grip again.

He realized he couldn't tighten the bolt. The threads were sheared, and even if he found the wrench, a rigid metal fix would only transmit the vibration more cleanly to the hull. He had to muffle the frequency. He had to absorb the sound.

He reached into his inner pocket and pulled out his last dry canvas wrap—a strip of grease-soaked fabric intended for the oars.

Working by touch alone in the freezing dark, Cormac wrapped the thick canvas strip around the copper pipe, binding it tightly at the point where it met the iron frame. He pulled the fabric taut, his teeth grinding as the rough canvas scraped against his raw, blistered fingers. He tied it off with a double hemp knot, using his teeth to pull the final turn tight.

He held his breath, listening.

The *clack-clack-clack* was gone.

The grease-soaked canvas had absorbed the physical vibration, dampening the frequency before it could travel into the hull. The copper pipe still trembled, but its movement was silent, muffled by the soft, oily layers of fabric.

Cormac lay in the freezing water for a long moment, his ear pressed against the wet wood of the keel. The vibration was dead.

Slowly, the high-pitched shriek of the ice needles above began to fade, dropping back down to a low, dormant hum before dying away into the absolute, heavy silence of the cavern.

He dragged his body back through the narrow hatch, his limbs heavy and unresponsive from the cold. When his head finally emerged from the floorboards, Toby and Garrick were staring at him, their faces pale, their eyes filled with a quiet, desperate relief.

Cormac pulled himself onto the deck, his wet caribou-skin suit dripping freezing water onto the timber. He wrapped Maeve's crimson woolen scarf tighter around his right wrist, his hand throbbing with a dull, persistent ache that he knew would never truly leave him.

He nodded once to Garrick.

*We're clear.*

Garrick let out a long, silent breath, his shoulders sagging as he guided the *Ember* around the final turn of the tunnel. The narrow basalt walls began to widen, the ceiling rising until the forest of glass daggers was lost in the high, dark vaults of the lower cavern.

They had survived the Screaming Glaciers. The boat glided out of the narrow hazard zone, sliding into a wide, slow-moving pool where the black water seemed to stretch out into the dark.

Toby Miller slumped against the main mast, his head back as he drew his first relaxed breath in hours. He pulled off his spectacles, wiping the condensation from the glass with his sleeve, a faint, trembling smile appearing on his face.

"We made it," Toby whispered, his voice a low, raspy thread in the quiet. "We're out."

Cormac didn't answer. He stood at the tiller, his eyes scanning the dark water ahead, his acoustic sensitivity still on high alert. The silence here was different—it was not the pressurized, fragile silence of the ice tunnels, but a deep, watchful quiet that felt heavy with an unseen presence.

Suddenly, a sharp, dry *thwack* shattered the stillness.

A silent, white bone spear, carved from the rib of a deep-water whale and tipped with a jagged sliver of volcanic obsidian, struck the wooden deck of the *Ember*.

It embedded itself four inches deep into the oak timber, its polished shaft vibrating violently.

It had missed Toby’s shoulder by inches.