Prologue

Boston, Seven Days Before the Eruption

JULIAN

The dead man’s heart beats at 2:13 in the morning.

I hear it through six inches of laboratory glass.

One slow impact. A pause. Then another.

The sound comes from the display case across the darkened geology lab, where a plaster cast of a victim from Pompeii lies curled on his side beneath museum lights. He has no heart. He has no flesh. He is a hollow made by ash nearly two thousand years ago, filled by archaeologists who wanted the shape of his final terror.

Yet the glass trembles with a third beat.

I set down my coffee.

On my monitor, the new thermal model of Vesuvius has stopped obeying physics.

The simulation should show a familiar sequence: pressure building beneath the crater, column collapse, pyroclastic density currents racing toward the ancient city. I have run versions of this model for sixteen years. Heat has rules, even when institutions do not. Rock fractures. Gas expands. Gravity wins.

Tonight the red plume on my screen turns sideways.

It threads through the digital reconstruction of Pompeii’s streets, avoids the forum, circles the amphitheatre, and gathers beneath a single human figure my software should not contain.

The figure is standing.

Broad shoulders. A raised arm. A shield that catches the simulated fire.

Across his chest, a chain of yellow marks flashes like a second nervous system. They begin beneath his sternum and spread outward in the branching pattern of a lava map.

Beat.

The display case shivers again.

I walk toward it despite every instinct telling me to call security. The cast is on loan from a private collection, labeled only NAMELESS MAN, PORTA NOCERA DISTRICT. The posture has always troubled me. He does not look as though he died hiding. One arm reaches forward, fingers curved around something the ash failed to preserve.

Tonight a black spot has appeared over his plaster heart.

I press two fingers to the glass.

It is hot.

My phone vibrates on the desk behind me. I do not have to look at the screen to know who it is. The university’s legal office has called three times this week, asking whether I intend to appeal the termination finding. The review panel called my delay a failure of professional judgment.

They were right.

Years ago, on another volcano, I let a sponsor soften my warning. The sensors were ambiguous, the evacuation expensive, the community poor. I signed a report that said monitoring should continue.

The mountain did not continue monitoring.

Forty-three people died before dawn.

I have spent every night since trying to build a model that can force frightened officials to act before certainty arrives. A perfect forecast. A warning no board can edit. A number powerful enough to make cowardice impossible.

The red plume on my monitor contracts.

Seven Days, the simulation writes.

The words are not part of my software.

Then:

FIVE THOUSAND MAY LIVE.

Another line burns beneath it.

ONE HEART MUST PAY.

I stare until the letters blur.

The lights go out.

Emergency power should switch on within two seconds. It does not. The lab vanishes into a darkness filled with the low mechanical hum of sleeping servers and the impossible pulse inside the display case.

Beat.

This one knocks a crack through the glass.

A filament of orange light leaks from the fracture. It smells of iron, sweat, hot stone, and something green crushed beneath a sandal. Not museum dust. Not ozone from faulty wiring.

Summer.

Crowds.

Blood on sand.

I step back, but the thermal camera above the case activates on its own. Its monitor shows my body in white and red. My pulse flashes at my throat.

Across the glass, a second heat signature appears.

The man inside the cast is no longer curled on the ground. In the camera’s image he stands directly behind the glass, alive and watching me.

He is unmistakably adult, perhaps thirty-five, built by labor rather than display—wide through the shoulders, scarred along one side, dark hair damp against his forehead. An iron collar circles his neck. His eyes hold the exhausted contempt of a man who has survived too many people calling his survival entertainment.

He raises his hand.

I raise mine without deciding to.

Our palms align on opposite sides of the cracked glass.

Heat slams through me.

For one instant I am inside another body. I feel a sword hilt rough against my palm. I taste copper where a tooth has split my lip. I hear twenty thousand people screaming for a death that belongs to someone else.

And beneath it all, I feel his heart.

Strong. Furious. Numbered.

Each beat falls away from a finite store, and somewhere beneath Vesuvius a corresponding chamber opens.

The man speaks. The glass should make sound impossible, but his voice arrives through my bones.

“Stop counting me.”

I snatch my hand back.

The connection breaks. The thermal monitor returns to a cold plaster shape. The black mark over the cast’s chest has grown to the size of a coin.

My computer prints a final line:

CASSIUS VARRO DIES AT SUNSET.

The name hits me with the force of recognition, though I have never read it. A memory opens where no memory should be: a stone corridor beneath an arena; a man chained to a wall; the mountain visible through an iron grate; my own hand pressed to his chest while ash turns noon into night.

I know what his final heartbeat feels like.

I know that I caused it.

The floor tilts.

Glass cases slide across the lab. Cabinets burst open. Seismographs chatter so violently their needles tear through paper. I drop to one knee, reaching for the desk, but the polished concrete beneath my palm has become rough volcanic stone.

Heat rushes up through the crack between worlds.

On the far side, Cassius is no longer behind glass. He stands in a sunlit arena, blood on his mouth, an iron chain dragging from his wrist. Vesuvius rises behind him beneath a perfect blue sky.

He looks directly at me.

“If you came to save us,” he says, “you are late.”

The lab floor opens.

I fall through ash, light, and nineteen centuries of regret.

The last sound I hear in Boston is the plaster heart beating once more.

The first sound I hear in Pompeii is a crowd demanding Cassius’s death.