The central station was a cathedral of rust. Steel beams arched over the tracks like the ribcage of a dead titan. Normally. it was a place of chaos. A sea of commuters and beggars. Tonight. it was a graveyard.
A heavy fog of grey ash drifted through the air. It settled on the benches and the ticket booths. It muffled the sound of the rain hitting the glass roof. The only movement came from the Sentinels. Elena Vance's new soldiers stood on the platforms. They were motionless. Their rifles were slung over their shoulders. They didn't need to look for intruders. They were waiting for a signal from the earth.
"The air is poison." Clara whispered. She pulled a wet rag over her nose and mouth.
Vane moved beside her. He was a shadow. The Sin-Eater's draught had worked. He felt light. He felt invisible. The heavy pressure of his family's history had vanished from his shoulders. But he was weak. His steps were heavy. His breath came in short. shallow bursts.
"The entrance is under the main clock." Vane said. His voice was a rasping ghost of his former authority. "There is a maintenance hatch. It leads to the steam tunnels. The well is below the water line."
They crawled beneath the shadows of a stationary freight train. Jax was a hundred yards away. perched in a signal box. His fingers were flying across a portable deck.
"I'm in." Jax's voice crackled through their earpieces. "The city's audio grid is mine. Give me the word."
"Now." Vane said.
A sound exploded from every speaker in the station. It wasn't music. It was the sound of a heartbeat. A slow. wet thud that vibrated the glass in the ceiling. Thump-thump. Thump-thump. The Sentinels on the platform jerked to life. Their heads snapped toward the speakers. The heartbeat grew louder. faster. It was the sound of the Blood Ledger. The sound of a thousand debts calling out to be paid.
"Go!" Vane hissed.
They ran.
They reached the maintenance hatch under the clock. Vane used a crowbar to wrench it open. The smell of mercury and ancient dampness hit them. They dropped into the hole. sliding down a slick metal chute.
They landed in a chamber that predated the city. The walls were made of black brick. The floor was a metal grate. Below the grate. a pool of liquid silver churned. It was the Mercury Well. The surface of the pool was not flat. It was a swirling vortex of metallic fluid. illuminated from beneath by a faint. sickly green light.
"It's beautiful." Clara said. She looked down at the silver. "And terrifying."
"It's the anchor." Vane said. He leaned against a pillar. his face grey. "The Vespers used it to ground the energy of the sacrifices. It's a lightning rod for the curse."
"Vane Vesper. You look terrible."
The voice came from the balcony above.
Elena Vance stepped out of the darkness. She was no longer wearing the grey suit. She wore a gown made of woven silver wire. Her skin was translucent. The grey ash had settled into her pores. making her look like a marble statue come to life. Her eyes were solid white.
Behind her. two Sentinels raised their weapons.
"Elena." Vane said. He didn't look up. He kept his eyes on the well. "You're late. The ritual is failing."
"The ritual is evolving." Elena said. She walked to the edge of the balcony. looking down at them with a cold. clinical hunger. "Silas was a fool. He thought the power belonged to the bloodline. He didn't realize the power belongs to the one who can endure the transformation."
She raised a hand. The liquid silver in the well began to rise. It formed long. shimmering needles that pointed toward Vane.
"You brought the girl back." Elena said. She looked at Clara. "The Final Key. I don't need a ledger to unlock the door. I just need her heart. When I drop her into the well. the city will never go dark again."
"You don't know how to close the circuit." Vane said. He moved toward Clara. shielding her.
"I don't want to close it." Elena smiled. It was a jagged. terrifying expression. "I want to become the circuit."
She made a sharp gesture. The Sentinels fired.
The bullets didn't hit Vane or Clara. They hit the metal pillars around them. sparks flying in the dark. It was a warning.
"Bring her to the edge." Elena commanded.
The Sentinels jumped down from the balcony. They moved with a mechanical precision. Their boots clanged on the metal grate.
Vane looked at Clara. He reached into his pocket and pulled out a small. heavy object. It was a shard of the original Blood Ledger's spine. It was a piece of bone. dark and ancient.
"The kill-switch." Vane whispered.
"How do we use it?" Clara asked. She was backed against the wall. the silver needles of the well inches from her feet.
"It has to be fed." Vane said. He looked at the bone. Then at her. "It needs a final name. A name that means something."
He took Clara's hand. He pressed the bone shard into her palm.
"Write it." he said.
"Write what?"
"Mine."
Clara shook her head. "No. Vane. There has to be another way."
"The well is a mirror." Vane said. His voice was urgent. The Sentinels were closing in. "It reflects the debt. If my name is written on the bone and thrown into the mercury. the ledger is satisfied. The Vesper debt is cancelled. But I go with it."
"Vane. please."
"Look at me. Clara." He took her face in his hands. He was old. He was dying. But he was the most beautiful thing she had ever seen. "I have lived two centuries of lies. Let me have one minute of truth. Save the city. Save yourself."
The Sentinels grabbed Clara's arms. They began to drag her toward the center of the grate. toward the swirling silver vortex.
Elena Vance laughed. A sound like breaking glass. "The time is now! The moon is at its zenith!"
Vane lunged at the Sentinel holding Clara's right arm. He bit. he scratched. he fought like a beast. He bought her a second of freedom.
"Write it!" he screamed.
Clara gripped the bone shard. She felt a sharp edge. She didn't have a pen. She didn't have ink. She used the shard to slice her own palm. The red blood flowed over the ancient bone. She used her finger to trace the letters.
VANE.
The bone began to glow with a blinding white light. It vibrated in her hand. a scream of energy that made her teeth ache.
The Sentinels recoiled. Their white eyes filled with cracks.
Elena Vance's smile vanished. "What are you doing? Stop her!"
Clara didn't wait. She ran to the edge of the well. She looked at Vane one last time. He was on his knees. a Sentinel's boot on his neck. He wasn't looking at Elena. He wasn't looking at the well. He was looking at her. and he was smiling.
"For the Underbelly." Clara said.
She threw the bone into the center of the mercury vortex.
The world went silent.
The silver liquid didn't splash. It froze. The shimmering needles shattered into dust. Then. a pillar of white fire erupted from the well. It didn't burn. It sang. It was a sound of a thousand chains breaking at once.
The fire hit the ceiling. blasting through the brick and stone. It traveled up through the station. through the tracks. through the very air of the city.
Every Sentinel in the station dissolved. They didn't die. They simply turned into grey ash and were blown away by the wind.
Elena Vance screamed. The silver wire of her gown began to melt into her skin. She was being pulled into the well. The power she had tried to steal was now a vacuum. sucking her into the void.
"Vane!" she shrieked. reaching out a hand.
But Vane was gone.
The white light was so bright Clara had to close her eyes. She felt the grate beneath her vanish. She felt herself falling into a warm. soft darkness.
When she opened her eyes. the station was quiet.
The Mercury Well was gone. In its place was a dry. stone pit filled with dust. The fog of ash had cleared. Above. through the hole in the ceiling. she could see the stars. They were white. The moon was a pale. normal crescent.
Clara sat up. Her head was spinning. She looked around the ruins of the chamber.
"Vane?" she called out.
There was no answer.
She crawled to the center of the room. She found his jacket. It was lying on the stone. empty. Beside it was the bone shard. It was white now. clean as a pebble on a beach.
She picked up the jacket and held it to her chest. It smelled of him. Of iron and incense and the rain.
She climbed out of the pit. She walked through the silent station. Jax was waiting for her by the maintenance hatch. He looked shaken. his neon hair standing on end.
"Is it over?" he asked.
"It's over." Clara said.
"Where's Vesper?"
Clara looked at the empty jacket in her arms. She looked at the city lights. which were beginning to flicker back on. one by one. Not the harsh. predatory glow of the tower. but the soft. warm lights of homes and streetlamps.
"He's home." she said.
She walked out into the rain. The Underbelly was waking up. People were coming out of their tenements. looking up at the sky. The shadow of the Zenith Tower was still there. but it was just a building. It didn't own them anymore.
Clara walked toward her father's house. She had a bone in her pocket and a heart that was finally beating for herself.
She didn't look back. But if she had. she might have seen a shadow standing in the entrance of the station. A shadow of a man with dark eyes. watching her until she turned the corner.