Then the external force that had created the pocket universe went into reverse, snapping shut the pocket and dropping the dense spherical crystal into the hole at the core of the star, less than thirty seconds after the bomb had gone off. And the gates of hell opened.

Iron doesn’t fuse easily: the process is endothermic, absorbing energy. When the guts were scooped out of the star and replaced with a tiny cannonball of cold degenerate matter, the outer layers of the star, held away from the core by radiation pressure, began to collapse inward across a gap of roughly a quarter million kilometers of cold vacuum. The outer shell rushed in fast, accelerating in the grip of a stellar gravity well. Minutes passed, and from the outside the photosphere of the star appeared to contract slightly as huge vortices of hot turbulent gas swirled and fulminated across it. Then the hammerblow of the implosion front reached the core …

There was scant warning for the inhabitants of the planet that had been targeted for murder. For a few minutes, star-watching satellites reported an imminent solar flare, irregularities leading to atmospheric effects, aurorae, and storm warnings for orbital workers and miners in the asteroid belt. Maybe one or two of the satellites had causal channels, limited bandwidth instantaneous communicators, unjammable but expensive and touchy. But there wasn’t enough warning to help anyone escape: the satellites simply went off-line one by one as a wave of failure crept outward from the star at the speed of light. In one research institute a meteorologist frowned at her workstation in bemusement, and tried to drill down a diagnostic — she was the only person on the planet who had time to realize something strange was happening. But the satellites she was tracking orbited only three light minutes closer to the star than the planet she lived on, and already she had lost two minutes chatting to a colleague about to go on her lunch break about the price of a house she would never buy now, out on the shore of a bay of lost dreams.

The hammerfall was a spherical shock wave of hydrogen plasma, blazing at a temperature of millions of degrees and compressed until it had many of the properties of metal. A hundred times as massive as the largest gas giant in the star system, by the time it slammed into the crystal of iron at the heart of the murdered star it was traveling at almost 2 percent of lightspeed. When it struck, a tenth of the gravitational potential energy of the star was converted into radiation in a matter of seconds. Fusion restarted, exotic reactions taking place as even the iron core began to soak up nuclei, building heavier and hotter and less stable intermediaries. In less than ten seconds, the star burned through a visible percentage of its fuel, enough to keep the fires banked for a billion years. There wasn’t enough mass in the G-type dwarf to exceed the electron degeneracy pressure in its core, collapsing it into a neutron star, but nevertheless a respectable shock front, almost a hundredth as potent as a supernova, rebounded from the core.

A huge pulse of neutrinos erupted outward, carrying away much of the energy from the prompt fusion burn. The neutral particles didn’t usually react with matter; the average neutrino could zip through a light year of lead without noticing. But there were so many of them that, as they sluiced through the outer layers of the star, they deposited a good chunk of their energy in the roiling bubble of foggy plasma that had replaced the photosphere. Not far behind them, a tidal wave of hard gamma radiation and neutrons a billion times brighter than the star ripped through the lower layers, blasting them apart. The dying star flashed a brilliant X-ray pulse like a trillion hydrogen bombs detonating in concert: and the neutrino pulse rolled out at the speed of light.

Eight minutes later — about a minute after she noticed the problem with the flare monitors — the meteorologist frowned. A hot, prickling flush seemed to crawl across her skin, itching: her vision was inexplicably streaked by crawling purple meteors. The desk in front of her flickered and died. She inhaled, smelling the sharp stink of ozone, looked round shaking her head to clear the sudden fog, and saw her colleague staring at her and blinking. “Hey, I feel like somebody just walked on my grave—” The lights flickered and died, but she had no trouble seeing because the air was alive with an eerie glow, and the small skylight window cast razor-sharp shadows on the floor. Then the patch of floor directly illuminated by the window began to smoke, and the meteorologist realized, fuzzily, that she wasn’t going to buy that house after all, wasn’t going to tell her partner about it, wasn’t ever going to see him again, or her parents, or her sister, or anything but that smoking square of brilliance that was slowly growing as the window frame burned away.

She received a small mercy: mere seconds later the upper atmosphere — turned into an anvil of plasma by the passing radiation pulse — reached the tropopause. Half a minute later the first shock wave leveled her building. She didn’t die alone; despite the lethal dose they all received from the neutrino pulse, nobody on the planet lived past the iron sunrise for long enough to feel the pangs of radiation sickness.

Wednesday hid under the desk, heart pounding with terror, clutching a stubby cylinder. She’d seen the body of the customs officer stuffed inside the darkened kitchen; realized he was dead, like the handwritten instructions in the diplomatic pouch said. Now the thing that did it was coming for her, and she wished -

There was a scratching click of claws on polycellulose flooring. I don’t want to be here, she prayed, fingers slipping around the sweat-lubed cylinder. This isn’t happening to me! She could see the hellhound outside, imagining it in her mind’s eye: jaws like diamond saw blades, wide-set eyes glowing with the overspill from its phased-array lidar. She could see the small, vicious gun implanted in its hollow skull, its brains governed by a set of embedded computers to override its Doberman instincts. Fist-sized overlapping bald patches, psoriatic skin thickening over diamond mesh armor. It could smell her fear. She’d read the papers in the strong room, realized how important they must be, and pushed the door ajar, thinking to leave — yanked it shut barely ahead of the snarl and the leap. Acrid smoke had curled up from the hinges as she scrambled into the ductwork, fled like a black-clad spider into the service axis and through the pressurized cargo tunnel and the shadows of the almost-empty dock, panting and crying as she went. Always hearing a scrabble of diamond-tipped claws on the floor behind her. I don’t exist. You can’t smell me!

Herman — as usual, when she needed him most — wasn’t talking.

The dog could smell her — or smell someone. She’d tabbed into a public term and watched the dog, or one of its cousins, stalk across the loading bay like the spectral, elongated shadow of a wolf — something born in frozen forests beneath a midnight sun, evolved to lope across the cyborg-infested tundra of an alien world. It had glanced at the hidden camera with glowing eyes, a glow that spun into static as it locked on and fired. It could sneeze nerve gas and shit land mines, if you believed her kid brother Jerm’s cheap third-person scripted arc-ventures; a product of a more sophisticated technosphere than Moscow’s, its muscles didn’t run on anything as primitive as actin/myosin contraction, and its bones were built for leverage — a hellhound running at full power hissed like a primitive locomotive, dissipating waste heat as steam hot enough to scald anyone who got too close.

She raised the riot cartridge, fingers tightening on the trigger switch, and pointed it at the doorway. Dim shadow of legs, too many legs. They paused, and the shadow swung across the wall, homing in. She squished down on the trigger and the canister kicked back at her hands as a terrible clatter rushed towards her and the air in front turned black. No, blue: like the dead man’s tongue, lying there. The paper said all but one copy of the data cartridge containing the customs transfer log were to be destroyed, and anyone who knew was to die. A tenuous aerogel foam bubbled and farted, rushing out into a ballooning mass as the dog lunged forward, teeth snapping, making a soft growling sound deep in its throat. It thumped against her feet in a soap-bubble cocoon, the growl turning into a deafening moaning howl of frustration.