The Thames ran black that morning, thick as tar and twice as foul. Thomas Graves woke where he always woke now—on the embankment near Southwark Bridge, his back against the cold stone, his left arm wrapped in linen that had gone from white to grey to something in between.

He had injected himself four hours ago. A vial of cobra venom, black as ink, bought from an Indian clerk in Whitechapel who did not ask questions. The dose was small—smaller each time, or so he told himself—but the marks were growing. Where the needle had pierced his forearm, the skin had bulged into dark knots, like something alive pushing against the surface. His face was worse. The scar tissue across his cheek and jaw had darkened overnight, the ridges raised and shiny as wet wax. He avoided the shop windows. He avoided mirrors entirely.

A siren wailed somewhere to the east. Whitechapel again. Graves closed his eyes and counted the seconds between the wail and the fading echo. Three seconds. Close.

He stood. The world tilted, then steadied. He walked north through the fog, which was thick enough to taste—coal smoke and river damp and something underneath, something old and rotting that the fog could not hide.

By eight o'clock he was at the Scotland Yard office on Broadway. Detective Crawford met him in a corridor that smelled of wet wool and pipe tobacco.

"You look terrible," Crawford said.

"Good morning to you too, Henry."

Crawford did not smile. He handed Graves a folder. Three photographs. A woman's shawl, torn and muddy. A child's wooden toy, found in the reeds. A length of rope, frayed at one end.

"Third one this month," Crawford said. "The press is calling it the River Man. I'm calling it a snake."

Graves flipped through the photos. His scar pulsed—a hot, thin line of pain behind his left eye. "Where?"

"Under the old tannery on Bermondsey Street. The drainage tunnel runs beneath it. We've sent two men in. Neither came back whole."

"How long has it been down there?"

"Since November. Maybe longer."

Graves nodded. He did not ask what the two men looked like when they came back. He had seen enough of that in India.

"I need a day," he said. "Alone. No one follows me."

Crawford studied his face. For a moment, Graves saw something like pity in the detective's eyes. Then it was gone.

"You have until sundown."

"I don't need sundown."

"Graves—"

"I said I don't need it."

He turned and walked away before Crawford could argue. He needed to stop at Agnes Webb's first.

---

The seamstress lived in a cellar flat on a lane so narrow the buildings on either side almost touched. Graves knocked twice, then waited. The door opened a crack, then wider. Agnes was smaller than he remembered, or perhaps he had simply grown larger—broader at the shoulders, heavier at the hips, a man accumulating weight the way a wound accumulates infection.

"Thomas." Her blind eyes were turned toward his voice, not his body. "You've been injecting again."

He did not answer. He sat on the stool she offered, and she took his arm in hands that were knotted with arthritis but steady as stone.

"The dose," she said. "How much?"

"Half a millilitre. Less than last time."

"Liar." She unwrapped the linen. The injection site was a black knot, swollen and shiny. Around it, the skin had taken on a greenish hue, like old bronze. "You're building up a tolerance. That's good. But the scarring—" She traced the air above his arm without touching it. "It's spreading."

"I know."

"You know nothing. You never did." She began to rewrap the arm in fresh linen, her fingers moving with the practiced efficiency of forty years at a sewing machine. "Thomas, when you were a boy—before the regiment, before India—you used to sit in the garden and watch the beetles. You'd watch them for hours, turning them over with a stick, watching them struggle. Do you remember?"

"I remember."

"You were seven. Your mother said you had a cruel streak. I told her you had a curious streak. I was wrong."

He did not respond. She finished the bandage and patted his shoulder.

"The thing under Bermondsey," she said. "Is it a snake?"

"Yes."

"Then kill it, Thomas. And come back to me afterward. I'll make tea. We'll sit in the kitchen, and you'll drink it, and you won't have to go back out there."

He stood. "I will."

"Thomas."

He paused at the door.

"You don't need to see the world with that face. Use your eyes."

He left without answering.

---

The tunnel beneath the tannery was wider than he expected—wide enough to walk upright, high enough that the ceiling disappeared into fog. He carried a single oil lamp, an iron tube, and a vial of concentrated cobra venom, this one full—two millilitres, the highest dose he had ever taken.

He walked for twenty minutes. The tunnel walls were slick with algae and something else—scales, thousands of them, shed over months or years, crunching under his boots like broken glass. The air grew warmer. Thicker. He could hear something ahead of him: a slow, rhythmic movement, like a body dragging itself through mud.

He set the lamp on the ground. Opened the iron tube. Checked the vial.

Then he knelt and extended his left arm into the darkness.

The cold hit him first—a wet, muscular cold, like a glove made of ice. Then the pressure, immense and sudden, closing around his forearm like a fist. He gritted his teeth and pushed deeper. The snake was pulling him in, and he was letting it.

His scar burned. The venom in his bloodstream was reacting—his body flooding with adrenaline, his heart hammering, his vision narrowing to a tunnel of white light. He could feel the snake's jaws around his arm, its fangs sinking through the linen, through his skin, into the muscle. Pain, white and absolute.

He held the vial against the wound and crushed it.

Venom met venom. Snake against snake. The ancient war, compressed into a single point of contact.

For a moment, nothing. Then the snake convulsed. Its grip loosened. Graves pulled his arm back—blood streaming, three puncture wounds weeping dark fluid—and swung the iron tube.

It connected with something hard and wet. A crack like a branch snapping. The snake shrieked—a sound no snake should make, a sound like a woman screaming through a throat full of water—and thrashed. Graves swung again. And again. Until the thrashing stopped. Until the only sound was his own breathing and the drip of water and the drip of something else.

He waited. Ten minutes. Twenty. Then he picked up the lamp and looked down at what he had killed.

It was larger than he had imagined. Thicker than a man's thigh. Dark green with a pattern of blotches that shifted and swam in the lamplight. Its eyes were open and clouded, like two coins dropped in a well. Its mouth was half-open, and inside it, something white and crystalline glinted—a capsule, sewn into the lining of its throat, the stitching torn by his venom.

Graves reached in and pulled it out. Small, no bigger than a thumb, made of glass and brass. He turned it over in his hands. Whatever was inside it, it was not meant for him.

---

He emerged from the tunnel at dawn. The fog was lifting, revealing the grey bones of London—the chimneys, the rooftops, the Thames running black and indifferent. He sat on the embankment and watched the sun struggle through the clouds.

His arm throbbed. His face burned. He could feel the venom working through his system, cleaning his blood, killing what needed killing, leaving whatever was left to scar over and harden.

A siren wailed in the distance. Closer this time. Whitechapel again. Or maybe Bermondsey. Or maybe somewhere else entirely—somewhere the fog had not yet reached, where the snake had not yet been found, where the next Thomas Graves was already waking on a riverbank, already reaching for a vial of poison.

He stood, brushed the mud from his coat, and walked into the city.

---