Though the meal of the lost child seemed to have satisfied the huge creature that had first stalked them, Emma glimpsed ridges of skin and yellow eyes everywhere. The crocodiles watched as the raft eroded, inevitably approaching the point where it would dump all its hapless inhabitants in the water.

Sally turned her head. With a cough, she threw up. Pale yellow bile splashed over Emma’s lap, stinking.

“Shit, oh shit.” She got hold of Sally’s leg, behind the knee, and strove to pull her over on her side.

The raft rocked, its component branches rippling, and the Runners hooted and snapped.

Emma ignored them. At last she got Sally on her side. She pushed Sally’s good arm under her head, with her broken arm on top of her torso, and one knee bent over so she wouldn’t roll back. She tipped Sally’s head back, hoping to ensure she wouldn’t choke, and was rewarded with another gush of vomit that splashed over her hands.

And now she became aware of another problem: a fresh stink, a spreading patch of moisture over Sally’s behind. Diarrhoea, obviously.

Fire hooted and held his hands over his prominent nose.

There wasn’t anything Emma could do about it, not for now. But it sure wasn’t a good sign. Perhaps it was blood poisoning: one touch of a filthy Runner finger in a wound, one splash of river water, might have done the damage. Or it might be something worse, some disease such as hepatitis or cholera or typhoid, or even some virulent nasty native to this ugly little world; she didn’t know enough about the symptoms of such things to be able to diagnose, one way or another.

And even if she did know what Sally was suffering from, what could she do about it? Her pocket-sized medical kit was gone, lost with the rest of her meagre kit as they had fled from the huge skin-clad creatures called Hams. She began to go through the pockets of her ragged, filthy flight suit, hoping to find even a single antibiotic tablet that had gone astray.

Sally convulsed again, and her vomit turned more clear, just a thin, stringy fluid.

Maxie, squatting with the other children, watched all this in wide-eyed dismay. He had been silent since they had left the shore, and now he watched Emma wrestle with Sally as if she were a side of beef, no doubt storing up more problems in that tousled, bewildered head. Later, Emma; one patient at a time.

After an hour of random drifting, the raft began to approach the river’s far shore. Shallow beaches strewn with purple-black pebbles slid by. More by chance than design, the Runners were completing the crossing of this huge, sluggish waterway.

Sand glimmered rust-red, a few feet beneath the surface, and it was snagging the raft’s branches. The raft creaked and spun. It began to break up, its component branches drifting apart. The Runners cried out. One skinny woman fell into the water with a fearful hoot.

“Emma!” Maxie came stumbling to her, his little feet plunging into brown river water. He threw himself into her arms, and she clutched him close.

More of the Runners fell into the water, or leapt away from the raft towards the shore, splashing noisily and yelling with fear. They seemed to have a lot of difficulty swimming, and Emma wondered if their heavily muscled bodies were denser than humans’. Wading clumsily, grabbing onto each other and their children, they began to flop out of the water and onto the beach, where they lay like sleek, muscular seals. They shook their heads to rid their tightly curled hair of water; droplets fell back to the river with eerie low-gravity slowness.

Emma felt cold water seeping into the legs of her track suit. Maxie cried out and squirmed higher up her body.

There was simply no way Emma was going to be able to get both Maxie and his mother across those few yards of deeper water.

Fire was one of the last to leave the raft. He actually stood upright on the raft, precariously, and its branches cracked and parted under his feet. Then, hooting, he leapt feet-first into the water. He staggered as his feet sank into the mud, but kept his balance. He looked down at the water lapping around his waist, as if amazed.

Emma called, “Fire! Help us. Fire. Fire Fire Emma Maxie!”

He looked around dully.

Emma held Maxie up above her head. The kid squealed and kicked; Emma wasn’t going to be able to hold him like this for long. She cried, “Fire Fire!”

Fire reached out with a liquid motion. With one hand he grabbed Maxie under his armpit and lifted him away from Emma, as if the child was as light as balsa wood. Then he turned and began splashing his way to the shore, holding Maxie high.

Without allowing herself to think about it — without even looking out for crocs — Emma pushed away the last branches, the last of the raft, and let herself and Sally slide into the water. Sally lay face-down in the water, passive, but Emma managed to roll her onto her back. The makeshift sling was filthy, stained by blood and the muddy river water. Emma got the inert woman’s head against her belly, and cupped her fingers under Sally’s chin. Then, working with her feet and her one free arm, she began to swim backwards, towing Sally’s floating form.

She was soon exhausted. Her soaked clothes were heavy and clinging, and her boots made her feet feel as if they were encased in concrete. It seemed an age before her kicking feet began to sink into a steeply rising river bottom. She stood up, gasping.

Sally was still floating, so Emma grabbed a handful of cloth at her shoulder and, still supporting her head, began to drag her out of the water. Nobody came to her assistance — nobody but Maxie, and he was more hindrance than help.

At last she got Sally out of the river, far enough that her feet were free of the lapping, muddy brown water, and she fell on her back with exhaustion.

On this side of the river, there was less evidence of the ash falls that had plagued the Runners for days. But beyond the narrow, pebble-strewn beach, the shore was heavily wooded. The Runners huddled together in suspicious silence, peering at the dense green banks above them.

Night was coming.

With barely a word exchanged, some of the Runners crept cautiously into the woods. Others walked down the beach, tentatively exploring, and Fire and a couple of the women began to drag branches from the edge of the forest, building a fire. Fire cast shy glances at Emma; evidently he remembered, in some dim way, how she had managed to start a fire even when he had lost his treasured handful of embers, probably a key moment in his tortured young life.

First things first, she thought.

She pulled Sally further up the beach. She turned Sally over once more to the recovery position, unzipped Sally’s trousers and with some difficulty wrestled them off her, followed by her panties. The clothes were filthy, of course, from faeces and river mud, and they clung to her flesh; but Emma was reluctant to use her knife — this was Sally’s only set of clothing in the whole world, after all. When she had the pants off she used handfuls of leaves to clean Sally up as best she could, and covered her with her own T-shirt, briskly stripped off.

Then, leaving Maxie with his mother, she walked briskly down the beach. After fifty paces she came to a small stream, decanting from some source in the forest. It had cut itself a shallow, braided valley. Two of the children were playing here, splashing and wrestling. Emma walked a little way upstream of them and began to rinse out Sally’s trousers and underwear in the shallow, sluggish water. When she was done she cleaned off her arms and hands, splashed cold water over her face, and took a deep drink. Then she dug her plastic bag out of her pocket — one of the few artefacts she had yet to lose — and dipped it to the stream to fill it with water.