I feel like I've been running for miles but I've slowed down now. I've reached the edge of town and there are fewer buildings and shadows to hide in. I don't want to be seen. I could have taken a car but there's nothing else on the roads now and I would have drawn too much attention to myself. I've lost track of time. It's early evening and the light has almost completely gone. I'm cold, soaked through by the heavy rain that's been falling for the last hour or so, but that's just a minor physical discomfort and I still feel surprisingly strong.

I don't know how long I've been outside now but so far I've seen only a couple of other people. The air is still full of noise as the military try to expose us and flush us out into the open but the streets are empty. I know there's supposed to be a curfew at night but I'm sure that's not the only reason why there's no-one around. Being out in the open is too dangerous. Those few people I have seen - the occasional solitary figure that creeps carefully through the shadows like me - I have kept away from. I don't want to risk making contact with anyone. Will they be like me? Perhaps they will but I can't afford to take any chances. They could be like the rest of them. I'll kill again if I have to but I'm not looking for trouble. Finding Ellis is more important. Tonight it feels as if the 'normal' part of the population have been driven into hiding in fear of us.

I think I'm probably about halfway between my flat and Liz's sister's house now. I had planned to walk all night but I think it will be sensible to stop and take cover soon. There are helicopters over the city again now and I feel exposed. Instinct tells me it'll soon be too much of a risk to be out alone in the darkness with the military swarming through the streets and the skies. If I thought it was safe to keep going I would. I'll take this opportunity to rest for a while and eat.

I can't stop thinking about Ellis. My poor little girl is stuck in the middle of a group of people who will turn against her at any time and without any warning. She's in danger and there's nothing I can do to help her. It might already be too late but I can't allow myself to think like that. I've consciously tried to block them from my mind but I find myself thinking about Lizzie, Edward and Josh again. Remembering them fills me with an overpowering sadness and remorse. I wonder if they might eventually change too? Could whatever has changed within me be buried somewhere inside them also? I'd like to believe it could but I don't hold out much hope. The government information I read earlier (if any of it was correct) said that just a small percentage of the population were likely to be affected. I sensed a difference between Ellis and the others too. She and I are alike. We're different to them, I can feel it. I have to accept that the rest of my family are lost.

I'm heading out of the city now. I look back over my shoulder and see that although there are still lights on in many buildings, there are also huge swathes of town which are bathed in darkness. The power must be down. It's inevitable, I suppose. This 'change' (whatever it is) might only be affecting a minority, but it's repercussions are being felt everywhere. It's tearing society apart as quickly as it destroyed my family.

I turn a corner and walk straight into another body coming the other way, the first person I've come across for some time. I immediately tense myself, ready for the kill. I push the dark figure back and clench my fists ready to strike. I stare through the darkness into the other person's face and... and it's okay. There is no anger, no hate and no threat. The mutual unspoken feeling of relief is immense. This person is like me and we both know that neither of us has anything to fear from the other.

'You okay?' I ask, keeping my voice low.

The other person nods and walks on.

***

I can hear engines in the distance. The military are still moving through the dark city behind me and they are closer now. There are more helicopters crawling through the sky too. I can see four of them hovering ominously, sweeping over the streets and occasionally illuminating the ground below them with impossibly bright spotlights. It's definitely time to get under cover.

I cross over a low stone bridge which spans a silent railway track. Ahead of me is the dark silhouette of a huge factory or warehouse and, on the other side of the road, a building site. As I get closer I see that it's the beginnings of a new housing estate. There are a few houses almost completed just off the main road and they are surrounded by the shells of other partially constructed buildings. The half-built walls and wooden frames jutting up into the air make it hard to tell whether the houses are going up or coming down. It's a silent and desolate place and it seems a sensible place to stop and shelter for a while.

The paving slabs and tarmac beneath my feet give way to gravel and dirt. I follow the muddy and uneven route deeper into the centre of the building site and find myself walking along a row of six homes of varying shapes, sizes and degrees of construction. The ground has been so badly churned by machinery here that it takes me a while to realise that I'm actually walking through the future back gardens of these buildings, not across the front. I wonder whether any of these houses will ever be finished now? The three furthest from me appear to be the most complete and I head towards them. Their windows and doors are covered with grey metal grilles. All except the middle one of the three. The grille which covered the space where its back door was intended to go has been prised off. It's lying on the ground in a puddle of mud, buckled and useless. I'm standing in front of the doorway now looking inside. Has someone been here? I realise that there could still be people inside but I need to stop. Should I go in? Is it safe? Sensing that no-where's safe anymore I climb the step and cautiously enter the building. If there is anyone in there and they're not like me I'll kill them.

Footsteps in the darkness. Sudden movement.

I try to move back but before I can react a figure is on top of me. My legs are kicked out from under me and I'm sent flying back across the hard concrete floor. I can't see anything. I try to kick and punch myself free and stand up but before I can move I'm knocked back down again. I can feel someone pressing down on my ankles and someone else has their hands on my shoulders, keeping me flat on the ground. There's a third person in here. I can see their shadow moving past the doorway.

'Think he's safe?' someone asks. They switch on a torch and the unexpected brightness burns my eyes.

'Turn it off,' I hear another one of them say in a loud, relieved whisper. 'He's all right.'

As quickly as the hands grabbed hold of me they now let go. I shuffle back across the floor, putting as much distance as I can between me and whoever else is in here. The light in the half-finished house is limited and I'm struggling to see anything. Someone's moving just ahead of me. I know there are at least three people in here but are there any more? The torch is switched on again.

'Take it easy, mate,' one of them says. 'We're not going to hurt you.'

I don't know if I believe him. I don't know if I believe anyone anymore.

The figure holding the torch shines the light into their own face. It's a man, perhaps mid-to-late twenties. I know instantly that he's like me and that I'm safe with him. And if this man is no threat then the people who are with him are no threat either.

'What's your name?' he asks.

'Danny,' I tell him, 'Danny McCoyne.'

'Been like this for long, love?' asks a woman's voice.

'What?' I mumble back.

'Been long since it happened?' she asks, rephrasing her question. I assume she's talking about what happened at home when I killed Harry and lost my family.

'Few hours,' I mumble, my throat dry. 'Not sure...'

'I'm Patrick,' the man holding the torch says, holding out his hand. I'm not sure whether he wants me to shake it or whether he's going to pull me up. I reach out and he helps me to stand. 'Happened to me three days ago,' he continues. 'Same for Nancy here. That's Craig,' he says, pointing the torch at the third person across the room. 'Yesterday afternoon, wasn't it, Craig?'

'Just after dinner,' Craig answers. Patrick shines the torch at him but it only illuminates a small part of a huge expanse of belly. Craig is immense.

'So what happened?' Nancy asks. 'Anyone close?'

'My partner's dad,' I explain, feeling some sadness but no remorse or guilt over what I've done. 'He just turned on me. Thought he was going to kill me so I...'

'Had to get him first?' she interrupts, finishing my sentence for me. My eyes are getting used to the darkness in the house now. I can see Nancy nodding and I immediately know that she completely understands what I had to do and why I had to do it, even if I'm still not sure myself. 'Everything will start to make more sense soon,' she tells me. 'I was just the same when it happened to me. Hated myself for doing it but I didn't have any choice. I'd been with John for almost thirty years and we'd hardly spent a day apart in all that time. It was just like someone had flicked a switch. I knew I had to do it.'

This is in danger of turning into a comedy of errors. Have they all killed? I ask the question without realising I'm speaking out loud.

'Suppose it just depends where you are when it happens,' Patrick says. 'Craig hasn't killed anyone yet, which is a surprise when you look at the size of the bugger!'

Nancy takes up Craig's story.

'Tried though, didn't you, love,' she sighs. In the circle of torchlight I see him nod. 'Bunch of them had you cornered at work, didn't they?'

'I was picking orders in the warehouse with four of them,' the giant of a man explains in a surprisingly soft voice. 'Didn't know what was happening. I started on one of them but there were too many. They shut me in one of the offices but I managed to get out of a window. All I could do was run.'

This conversation is bizarre and uncomfortably surreal. It only becomes believable again when I remember the fact that I've killed twice today. How could that be? Christ, until this morning I hadn't even hit anyone in temper, let alone killed them. Patrick passes me a bottle of water which I drink from thirstily.

'What about you?' I ask him.

'I killed,' he answers. 'Don't know who the guy was, I just had to do it like the rest of you. He was just stood there staring at me as I was getting into the car...'

'...and?''

'And I mowed him down. Started the engine, chased him down the street and I mowed him down. Pretty much wrote the car off too. Just kept driving along with him under the wheels. I didn't know what else to do. Tried to go back home but when I got there I saw that my girl was just like the rest of them and...'

'...and you know the rest of the story,' Craig grumbles. 'You just have to do it, don't you?'

'It feels like second nature,' Patrick says quietly. 'It's instinctive. It's animal instinct.'

The room falls silent.

'So what happens now?' I ask.

'Who knows,' Nancy answers. 'My guess is we'll just keep killing each other until either we're all gone or they are. Crazy, isn't it?'

It's hard to get my head round the fact that this woman (who looks like any other average wife / mother / daughter / sister / aunt) is talking so matter-of-factly about killing. In the days since she's changed she seems to have relinquished every aspect of her former life and is now prepared to kill to stay alive herself. At moments like this it all seems beyond belief. Nancy looks more likely to bake you a cake than kill you. I shake my head in bewilderment as Craig gets up and drags a wooden board across the open doorway, blocking out the last shards of light coming in from outside.