One

there weren't enough live bodies to cope with emergencies. You could hardly term it an acceptable level of collateral, but there were no feasible alternatives. There were no rapid response units, no electric-blue lights or souped-up engines. Nobody warned you about the dangers; everyone knew the score. The people screaming were either slowed down by injury, or the weight of the things they were carrying, or, Jane wrote: because they want to be caught.

He looked at the things that he took with him everywhere. Once it had been a wallet, a shoulder bag for his bottle of water, newspapers and novel. Now money meant nothing and he himself was the news. Reading novels seemed offensive, somehow, in these times; an insult to the people who had been killed. Books had once seen him through many a grim hour flushing his system of nitrogen on the Ceto, so long ago that to think of diving was to somehow question his own sanity. Hundreds of feet deep, wearing only a thin rubber skin and a helmet? It was work from nightmares. It was behaviour from one of the science fiction novels he'd read.

The mantra he had once uttered, getting ready in the morning, had been keys, money, bus pass. Now it was rifle, mask, goggles. The rifle, its walnut stock having changed its shape minutely over the years where he'd held it so that it might fit his own hand better, was an old friend; he felt as naked without it over his shoulder as he would if he'd forgotten to put on his boots. Filters for the bicycle mask. Sunblock. His bible. The new essentials. Not heavy now, but maybe they would be one day when age was piling into him, or a muscle strain had halved his walking speed.

I no longer know what day it is, Stanley, or what time of day. I know when it's time to wake up and when it's time to go to sleep. It's kind of nice. I remember everything being geared to the clock and the watch when I was younger. Everything was an appointment. Getting you up and to nursery on time, if I was off duty. Picking you up in the afternoon. Tea by five, bath by six, bed by seven. Do you remember the game we played once, Stan? Last man on Earth, I called it. But you said you wanted to call it One. You said it was more serious to do that. More grown-up. You were really into your numbers. What's a hundred add a hundred add one, you'd ask me. And I'd pretend to struggle, and you'd tell me the answer.

And I asked you, what would you do if you were the last person on Earth, the One, and you said you'd get into a rocket and fly off to another place to live. And I asked you, what if there were no rockets, and you got upset and started crying and it took me a long time to get you to calm down and your mum gave me a hard time for it, but I cuddled you and you stopped, you fell asleep in my arms and I held you for ages. I was going to put you to bed, we were on the stairs, and you woke up and smiled at me and gave me a kiss, and you said to me, Stan, you said to me that it would never be One, because we were together all the time. You said we'd been meant to be together all the years I'd been me without ever knowing you. And it's true. Ever since you came into my life I can't remember before it. Which sounds silly. I mean, I know I lived for thirty-odd years before we had you, but they seem so pale and pointless. I came into being at the same time you did, my gorgeous boy, my Stan. And you are always with me. You kept me alive for so long. You keep me going.

So we're here and it's now, maybe ten years since I last saw you, you a big boy now, already at the end of school and thinking about sixth form, maybe, and we're playing One for real. Well, it's not properly One, because there are some of us left. You too, I'm hoping. You and Mum, I'm praying every day that's the case. Things are dangerous, Stan.

And sometimes I hope you went fast. Right at the start of things. With no danger of ever being alone and afraid, your innocence being torn to meaninglessness. I hope you did not suffer.

Jane's pen hovered above the journal; he was unable to form into words what he doubted his son would ever understand anyway. Instead, he returned to his survey of this corner of the city. For maybe the thousandth time he counted the cars and buses that were ranged around Trafalgar Square. Forty-eight cars, including taxis; nine vans of varying size; one coach (what a day trip that turned out to be); twelve buses. Seven motorbikes. He remembered photographs he had seen of various parts of London, miraculously free of traffic. Dogs and horses and carts. One or two automobiles driven by people who had nowhere to go and few roads on which to take their shiny toys. Sheaves of mud and dung peeled to one side by thin wheels. Now, unless you were walking at night and alert to possible hiding places, you could easily miss the vehicles that cluttered the streets. Even if somebody could be bothered to shift them, their ghosts would remain in the parts of the road shielded by metal and cellulose like the outlines of bodies at the scene of a crime.

There were twelve buses ranged around Trafalgar Square. One of them was on its side. Four of them were black where fire had turned them to shells. A Brixton bus for ever veering left to travel down Whitehall had been turned into an armoured safe house. Steel braces had been bolted onto the sides of the bus and dug deep into the earth under the tarmac, to prevent anything from pushing it over. Steel shutters protected the empty frames of the windows. During the daylight hours, when few Skinners were seen, the people who lived in this tank would come out to fortify the braces where they had begun to be excavated, and reposition the thickets of barbed wire that had been pulled away in the night. Jane envied them their stoicism, but could not have done the same thing. All those weeks of walking down to London had instilled in him a fear of standing still, even for a short time. Although he liked this spot, he grew itchy after just quarter of an hour, and had to quell the instinct to get back on the road. This was orange. This was safe. For now.

Cold was creeping through the blanket and the fleece of his coat into his legs. Jane stopped writing and stood up, wishing for a flask of something hot. He did some exercises, unhappy with how quickly he grew tired and breathless. He made himself cough into his fist and inspected his sputum. Each time he did this he was braced for flecks of blood but they never came. His breath smelled rotten, though, and he knew this was due to some failure in his teeth, the decay he had felt working its way through his mouth for years. As for the rest of him, sometimes when he moved he caught a whiff of how ripe his flesh was, but that was true of everybody. Washing was a luxury. Sometimes he took cold showers if he could find a working spigot and a compliant pump. Mostly he went without. His hair hung in damp ropes. He'd tried to cut it once, but there was no point. You felt you could never get dry. Dirt was ingrained in the contours of your fingers, these fingers that had once touched the pulse in the wrist of a sleeping child. Your hands became maps of all the places you'd been, digging through the filth to get to something or get away from it. You lost sight of who you were and where you came from. You failed to recognise things and they began to matter less.

He tended to keep many of his clothes on these days; he had enough to worry about without the shock of his own emaciation. Resources among the Shaded were growing scarce; soon they would not be able to offer any kind of reward for this work. He foresaw a future of blank pages. Hunger eventually blotted out all other thought. You couldn't write if you were going blind with the need for sustenance.

Jane knew he was following a dark path with all this negativity. He could see where it was leading him. It was a case of how far he was likely to travel. How much distance was there between forgoing basic hygiene and swallowing the pill of Stanley's death?

He spent three hours on the rooftop of the ENO building – hoping that Aidan might stop by this way – before the rain came back and he spotted the tiger, drifting like smoke out of Northumberland Avenue. He saw it pad across to Canada House, where it sat and washed its paws, gazing at its frozen brethren. Jane clenched his teeth and felt the gums in his jaw shift like a thumb pressed into sponge. He delved for positive images, the bright, shiny packages wrapped up with string that he turned to when it seemed he must go under. He wanted to believe that he always felt like this during Library duty; not because of the bad memories that it necessarily forced you to dredge up, but because it always presaged the worst job he had ever had. Plodding through frigid, alien fathoms in utter darkness in order to weld closed any number of fatigue cracks was a doddle compared to incineration duty.

But nothing he could fasten on, bar Stanley, ever repelled the misery. Peacock feathers found under a slurry of ash and black slush in Holland Park. A tray of glittering butterflies rescued intact from the looted squalor of the Natural History Museum. A can of Guinness discovered inside one thigh-high PVC boot in a BDSM dungeon in Kentish Town. It was all just a different kind of dust. It was as if, resorting to his son – every day, every hour, every other minute – was diminishing him. He was using Stanley up, like a pencil. There was nothing but a stub left, it seemed. He dreamed sometimes of his boy and he appeared so tired, so exhausted by his father's demands that every rise of his ribcage had to be his last.

He watched the tiger slowly, almost lazily, pull itself on to all fours once more. He saw the great head swing his way, making hesitant curlicues as it sniffed the air, the jaws hanging open to aid its sense of smell. The wind was blowing up from the Thames today; his scent was being pushed in a different direction. Still, it terrified Jane to see the muscled hulk of three hundred pounds of big cat – or whatever filled the space it had once owned – working hard to draw Jane's taste into its flavour chambers, pausing as if unsure of what the weather was telling it.