And now a missile shape rose before him, a great mouth gaped white, and through the murky water he could see rows of conical teeth. He flailed back.

The crocodile had lain at the bottom of her lake, silent, patient.

A distant cousin of the seagoing deinonychus, so far the events of this tumultuous day had meant little to her. She had felt the shuddering of the Earth and the responding ripple of the water, noticed the peculiar lights in the sky. But she expected to ride out this storm, as she had ridden out many before. She could stay underwater for an hour at a time, as her metabolism was capable of shutting down almost completely when necessary. Her thinking was slow, patient. She knew that all she had to do was lie here in the mud, and the storm would pass, and once more her food would come to her.

But now a dinosaur came blundering clumsily into the water — not just skimming the fringe to drink and browse, like the stupid duckbills, but immersing itself, actually swimming in her domain. She felt anger at this intrusion, mixed with anticipation at any easy meal. She pushed herself away from the mud and rose toward the surface, which glimmered with meteor light. But more massive bodies plunged helplessly into the turbid water, struggling in the clinging mud of the lake bottom.

She attacked, of course.

Giant thrashed, evading the crocodile’s reaching jaws, and in his blundering he managed to land a kick on the crocodile’s snout. The crocodile backed away briefly. But soon she was returning to the attack. Giant might have withdrawn. But a crowd of animals was pushing into the water behind him. The crocodile fought and snapped at the invaders; and the animals warred amongst themselves.

But now there was a mighty surge, as an aftershock of the comet’s seismic jolt shuddered through the basement rock. The ground was uplifted, cracked — and the water drained suddenly away, leaving Giant stranded amid drying vegetation and writhing animals.

The crocodile, suddenly exposed to hot, dry air, could not understand what had happened. She tried to burrow into the mud, instructed by instincts that had guided her as a baby from her shell to her first swim. But the mud was hardening, drying fast; she could not even dig into the ooze.

Still the meteors fell, lancing through the clouds of smoke like pillars of light.

The winds and the tsunami had already wiped out most of the living things, from insects to dinosaurs, in North and South America. Around the world, the gathering fires were now killing most of those who had survived.

But the worst was yet to come.

The coarser ejecta at the periphery of the comet impact had fallen back quickly, much of it pounding the disturbed ground within one or two diameters of the central crater, the rest falling as forest-igniting meteors. But the great central plume of rock vapor had continued to rise, propelled by its own heat energy. In the vacuum of space, solid particles condensed out of this glowing cloud, and, still white-hot, began to fall back to Earth. But where they had risen through a tunnel of vacuum, now they fell back into atmosphere, and they dumped their energy into the air. It was a lethal hail of fire, a planetwide blanket of uncounted billions of tiny, white-hot meteors.

All over the planet, the air began to glow.

Purga had reached a foothill. Her mate, Third, and her one surviving pup were at her side. They could go no further toward the true Rockies, for even here the land had been broken and jumbled by the ground waves, littered with boulders that were many times Purga’s height.

This would have to do. She began to dig into the loose dirt, seeking to build a burrow.

She glanced back the way she had come. Under banks of billowing smoke the whole of the land glowed bright orange; it was an extraordinary sight. Even here, on this rocky rise, she could feel the heat; even here she could smell the stink of smoke and burning flesh.

She could see the clouds that had drawn her here. They were ragged, but still clustered around the upper slopes of the mountains. Against a sky as black as night the clouds glowed orange white, reflecting the glow of the burning land. But now, beyond the clouds, that orange light from the south crept overhead. The sky itself began to glow, like a dawn erupting all over the sky, all at the same time. The color quickly escalated to orange, then yellow, then a dazzling white, sun-bright.

The heat’s first breath reached them.

The primates scrabbled desperately at the ground.

On the cracked pond floor Giant was somehow on his feet, surrounded by the dead. He couldn’t breathe; his chest strained at air that was dense with smoke and bits of glowing, charred vegetation. It was like being in a gray fog. He saw nothing but smoke, dust, swirling ash.

Heat pulsed, hot as an oven. There was a stink of burning meat.

He felt a sharp pain in his hand. He lifted it in dim curiosity. His fingers were burning, like candles.

His last thought was of his brothers.

His death came in a moment of fulminant shock. He knew nothing about it: His vital organs were destroyed too quickly for his brain to process a conscious reaction. Then his muscles cooked and coagulated. They contracted his arms and legs, but his spine was extended, so that in this moment of death he adopted a posture oddly like a boxer’s, head back, hands up, legs flexed. His flesh was seared away, and the enamel on his teeth began to shatter.

All this before Giant had time to fall to the ground.

And then the very rocks began to crack.

Jewel-like, its sudden brilliance reflecting from the ancient seas of its companion Moon, Earth was beautiful. But it was the beauty of a dying world.

Half of all the heat energy released by the burning air was injected into the deeper atmosphere and the ground. All over the planet, the sky was as hot and bright as the sun. Plants and animals burned where they stood. The trees of the mighty Cretaceous forests were consumed like pine needles. Any birds in the air disappeared in a puff of flame, and the pterosaurs vanished into the maw of extinction. The burrows of mammals and insects and amphibians turned into tiny coffins. Purga’s second pup, whimpering and alone, was quickly baked.

Purga was spared. The last clouds, shadowed black, became ragged, dispersing quickly, soon vaporized into steam — but for the crucial minutes of the great heat pulse they served to shield the ground beneath them from a sky as bright as the sun.

It was just an hour after the impact.

After the first few days the Earth’s shuddering died away, and the daily stamping of the great mountain-reptiles was gone.

Purga was used to darkness. But not to silence, this eerie stillness that went on and on.

For countless generations the dinosaurs had framed the lives of Purga’s kind. Even after this cataclysmic shock, she had vague visions of arrays of dinosaurs waiting in silent rows to trap any mammal unwise enough to poke her snout out of her burrow.

But she could not stay here, in this hasty burrow. For one thing there was nothing to eat; the family had quickly excavated and consumed any burrowing worms or beetles they could reach. They didn’t even know when it was day and when it was night. Their sleep cycles had been thrown off by their flight during the day of the impact, and they found themselves waking at different hours, their hunger conflicting with their fear of the strange, cold silence above. They bickered among themselves, snapping and biting.

And as time wore on the temperature plunged, from the intense heat of the hours of the burning sky to a bitter cold. The primates were sheltered by the thick layer of earth above them, but even that would not protect them forever.