The glass book in my hands glowed brighter.
Light spilled between my fingers, ran along the faint seams in the cover, and sank into the page like water sinking into sand.
If you must choose, save one who looks away.
The boy's foot slid across the seam. He was still watching the flock of clear birds above the far tower. They moved in perfect spirals, their wings catching the light in brief flashes of silver and ice blue. He laughed, the sound bright and innocent, a sound that did not belong here, not with the wrong note humming under us.
His mother was only a step away, but her eyes were on the birds too. She reached without looking, catching nothing but the fabric of his sleeve as he edged backward toward the open air.
The wrong note deepened. It had a weight to it now, a vibration that sank into my jaw and made my teeth ache. The seam gave a soft, sharp sound, almost like glass sighing before it decides to shatter.
I moved.
The people nearest me turned to see why I was leaving the safety of the balcony rail. They stepped back as I passed. I heard Iven's voice call my name — sharp, short — but I did not stop.
The book stayed in my left hand, pressed hard to my ribs. My right arm hooked over the outer railing as I crossed onto the bridge.
The glass was smoother than I expected. It gave just a little under my boots, like stepping on a frozen pond with water moving far below. The hum of the span vibrated up through my legs and into my chest. Each step felt heavier than the last.
The crown of the bridge was still ten steps away from the boy. Lio stood three steps beyond him, crouched low with one hand pressed to the seam, her head tilted as if she were listening with her whole body. She had not seen him yet.
I counted the steps in my head.
One… two… three…
The seam trembled again. The hum caught in my breath.
The boy's heel slid another inch. His balance tilted toward the empty air.
Four… five…
Lio turned then. Her eyes flicked to me, then to the boy, and widened in alarm.
"Move," she said sharply, but I was already moving.
I dropped to one knee and slid the last step forward. My hand caught the back of his shirt just as the seam under his foot gave a long, thin crack.
It sounded like ice breaking on a winter river.
A white fracture shot outward from the point where he had stood. It split into two lines, each humming a note that jarred against the rest of the span.
Gasps rose from the crowd on both towers. I felt the air shift as people stepped back from the railings.
The boy froze in my grip, stiff as a caught bird. I pulled him toward me, steady and slow, not daring to jolt the fractured seam any further. His mother's face had gone pale. She stepped onto the glass with hesitant feet, her hands shaking as she reached for him.
When she took him into her arms, she pulled him close enough that his face vanished against her shoulder. She whispered something over and over, words too soft to carry through the hum of the bridge.
"Back," Lio's voice called. "All of you. Now."
We moved together toward the nearest tower. The seam groaned again, a low, dangerous sound like a rope fraying under tension. The light along the rail flickered twice.
Once the boy and his mother were safe on the deck, I turned back. Lio was still crouched at the crown. Her palm rested flat on the fractured glass, her hair shifting in the wind.
"I can feel it," she said without looking up. Her voice was tight. "It wants to go."
Iven had reached the deck. He was already signaling to the operators on both sides. Clear ropes were unspooled and anchored to the railings.
"Brace it," he ordered. "Now."
The book warmed again in my hands. New lines etched themselves across the page, the glow fading as the words settled.
Do not run.
Do not lie.
Do not touch the seam with your right hand.
I folded my right hand into my sleeve. My palm felt cold.
Lio glanced over her shoulder at me. "Row… get off the span."
Another crack rang out, sharper this time. A section of glass near the far end of the seam shivered. People there began to shout and wave at those behind them to move.
The hum had changed. It was no longer a steady background song. It had the uneven throb of something breaking apart in slow motion.
I stepped closer to Lio, careful to place each foot where the glass still looked clear. "What happens if this seam fails completely," I asked.
Her eyes met mine for the briefest moment. "The bridge goes," she said. "And maybe the ones tied to it."
The far tower operator shouted something I could not catch. Iven's reply was lost in the wind. The ropes they had anchored went taut, pulling against the span as if the bridge were an animal straining at a leash.
The boy's mother had not left. She stood at the deck's edge, still holding him. Her gaze darted from me to the crown to the far side of the bridge, where people were now hurrying to get off.
The seam groaned again, louder this time, and I saw the crack widen by the width of a hair.
The book pulsed with heat.
Another line of writing appeared.
If you must choose, save one who looks away.
I scanned the crown. Lio was steady, her hand still on the fracture. She was watching the glass, not the crowd. Her weight shifted slightly as she felt for the next change in the hum.
Then I saw him — another child, older than the first, lingering halfway down the span. His friends had already reached the far tower, calling for him to hurry. He glanced at them over his shoulder… and then turned his head to stare at the same birds the younger boy had been watching.
His foot angled toward the seam.
The light along the railing dimmed.
The hum dropped to a low note that I could feel in the back of my throat.
The crack at the crown whispered… then screamed.