More barely remembered medical lore came back to her. Diarrhoea and vomiting led to dehydration, which you ought to treat with sugar and salt, a teaspoon of each to a litre of water, if she remembered right. Fine, save that she had no sugar or salt, and no teaspoon for that matter…

She glanced up the beach.

Stone was squatting beside Sally. He had removed the T-shirt from her lower body, and was running his hands up her thigh. Maxie had cowered back to the edge of the woods, watching the huge man grope his mother.

Emma put down the water, straightened up, and began to walk back to Sally. She felt around her neck for her Swiss Army knife. She got to within a foot of Stone without him noticing she was there.

So where are you going to stick your blade, Emma? In his cheek, his rock-hard penis, his back? What makes you think this tiny little bee-sting blade will do more than goad him anyhow? He’ll kill you, then do what he wants with Sally anyhow.

She pulled out the foldaway lens and lifted it up. She angled it so she caught the sun, and focused a bright spot on the back of Stone’s broad neck. He howled, slapping his neck, and jumped up, whirling, his penis flopping. As calmly as she could she tilted back the lens so the spot of light shone in his eyes. He raised his hands, dazzled. She said, “Keep away from her. Stone, you asshole, or I will bring down the sun on you. Stone sun Stone sun! Understand?”

He growled, but still the light shone in his eyes. He stumbled away, his penis wilting.

Trembling, trying to give an impression of command, Emma walked back along the beach, picked up her bag of water, and hurried back to Sally.

Sally still lay on her side, her head resting on her good arm, eyes closed, mouth open. There was a bubble of saliva at her mouth. That bubble of saliva popped, abruptly.

“Oh shit,” Emma said. She grabbed Sally and pushed her on her back. Sally sighed once, and then was still. Emma pinched Sally’s cheeks until her lips parted. The skin was cool and waxy. She dug her fingers in Sally’s mouth, and scooped out gobbets of vomit and flung it on the sand. Then she placed one hand under Sally’s chin and tilted her head back. She could hear no breath, not a whisper.

She ran her hands over Sally’s torso, seeking the end of the breastbone. Then she pulled her hands to the middle of her chest, placed the heel of her hand a little higher, and began to press down. “One-and-two-and…”

A child leapt out of the woods, a lithe hairy child, its face twisted into a snarl. Maxie scrambled away, screaming. Emma shrank back from Sally, gasping with terror.

…No, not a child. It was an ape, an adult — a female, in fact, with two small empty dugs, a skinny, naked body covered in spiky black-brown hair. She was maybe three feet tall. She had the face of a chimp, with lowering eyes gazing out of ridged sockets, and a protruding mouth with thick wrinkled lips covering angular teeth. Emma could have cupped her brain pan in one hand. But she walked and ran upright, human-style, like a clumsy mannequin — her feet were more human than not — and in one curved, bony hand, dangling below her knees, she clutched what looked like a shaped pebble.

She was a caricature, a shrunken, shrivelled, spellbound mix of ape and human, a dwarfish sprite: an Elf, just as the Runners called her kind. This ape-woman ran up to Emma and capered before her.

Emma picked up a handful of sand and hurled it in the Elf’s face.

The Elf howled and staggered back, rubbing her eyes.

Fire came running out of the forest’s shade. With a single, almost graceful swipe, he slammed a rock against the side of the Elf’s head.

She fell sprawled on the beach, unconscious or dying, half her face crushed.

Now there was screaming and yelling. All along the beach. Elf-folk were boiling out of the forest. They ran along the shore, rocks and sticks in their hands.

But the Runners fought back hard. Mothers grabbed their children and ran into the sea, where the Elf-folk seemed reluctant to follow. Men and women threw rocks at the scampering Elf-folk, and swung at them with their fists and feet.

But there were many, many of the Elf-folk, and they fought with a mindless intensity that seemed to overwhelm even the Runners.

Emma, trying to ignore this hideous drama, threw herself back at Sally.

After fifteen compressions Emma pinched Sally’s nose, clamped her mouth on Sally’s, and breathed hard and deep. She tasted vomit and blood. She pulled her head away, let Sally’s chest deflate, and tried again. After two breaths she searched again for a pulse, found none, and slammed the heel of her hand into Sally’s chest once more.

The conflict went on, crude, animal-like.

It’s not my battle, Emma told herself. These aren’t people. If they are humans at all they are some kind of predecessor species. Really, they are just two breeds of animals fighting for space. But one breed was at least hollering simple words — “Stone!”

“Stone, Blue, Blue!”

“Away, away!” — and she couldn’t help a deep sense of gratification every time one of those spindly Elf bodies went down, under Runner fists and feet.

Now Stone broke out of the squabbling pack. He had two Elves clinging to his back. One had its teeth sunk into his shoulder, and the other had torn off part of his scalp and a section of his right ear. Stone was howling, and blood poured over him from the glistening crimson wound in his head. More Elves swarmed over him, scratching, biting and beating. Stone went down, and rolled over into the water.

Emma heard an anguished scream. A woman burst out of the squabbling pack. It was Grass. Some of the Elves had closed in a pack around something that struggled, yelling, brown limbs flashing. It was a Runner child — perhaps Grass’s child. Grass threw herself at the Elves” backs. They drove her off easily, but she came back for more, twice, three times, until at last a chipped rock was slammed against the side of her head, and she fell to her knees, grunting.

The Elf-folk slid into the forest with their prize, their screeching cries of triumph sounding like laughter.

…And still Emma could find no pulse. She sat back, arms hurting, lungs aching. She was aware of Maxie watching her, a little pillar of desolation, ominously silent. “Oh, Maxie, I’m sorry.”

Stone was still in the water, on all fours, head lolling, his hair soaked, the water swirling crimson-brown under him.

Fire stood over him. He was holding a boulder, Emma saw, a slab of worn basaltic rock as big as his head.

Stone looked up, blood congealing over one eye. He raised a hand to Fire, reaching up for help.

Fire slammed the rock down on the crown of Stone’s skull. There was a sound like a crunching apple.

Stone slumped. Thick red-black blood diffused in the water.

Fire stood staring at the body. Then he turned to Emma. His gait and eyes held a glittering hardness she had not seen before. She shrank back, scrambling over the ground, away from Sally’s body.

Fire squatted down before her. His powerful, bloody fingers brushed her neck. She shuddered at his touch, feeling the burn scars on his palms. He pushed his hand inside her flight suit, and his hand closed around the Swiss Army knife. The lens was open. He snapped off the lens attachment as if breaking a matchstick.

Fire looked at the lens, and at Sally’s body, and at Emma. Then he backed away from her, stinking of blood.

Maxie was a few feet away, backed up against a tree. His gaze was sliding over Runners, blood-stained sand, the river.

Emma stood, cautiously. Keeping her eyes on Fire, she reached out for Maxie. “Come on, Maxie. This is no place for us, not any more. It never was…”

“No!” Maxie pulled away from her, his face twisted.

She thought, Now I’m the woman who killed his mother. Nevertheless, I’m all he’s got. She made a grab for him.