The journey back to Green Park Tube Station was eerily quiet and without incident.

Any mission topside was eerie, now that London was dead, its carcass still barely ripe for picking, but it was rarely without incident. Even now, when Grey activities within the city seemed somewhat scaled back, it was unusual to venture anywhere without at least one sighting.

Today, it was as if they were no longer here. As if they had upped and left in the night.

The only sign that they were very much still here, was the ominous dark wall of cloud that marked the edge of the Black Zone. Even on a searing hot summer's day, the cloud remained, a thick ashen barrier surrounding the outer limits, blocking visibility of their giant monolithic crafts hanging in the air over Westminster and Buckingham Palace. It wasn't impenetrable by any means, as Lena and Tom had testified in their account of venturing close to Central Hall, but just the sight of it was enough to stab an icy cold shard into your chest.

It looked similar in height and depth to a shelf cloud, a strange weather phenomenon that usually marked the start of an oncoming thunderstorm, only there was no storm coming our way this time.

The storm was already here, hidden inside, obscured from view.

Ordinarily, the Black Zone cloud was the blot on the landscape, the one thing I tried not to look at because of the uneasy feeling it stirred in my stomach, and yet I was unable to banish it from my field of vision. No matter how hard I tried, it was always there, an ever-present darkness in the corner of my eye.

Today, however, it wasn't the cloud that darkened my line of sight.

It was him.

The Grey.

I felt haunted by him. I felt haunted by the ghost of my husband, knowing that he was dead and yet not dead, his face and body stolen by the ghoul by my side, that seemed intent on dogging my every step. Every time I looked at him - which I was trying desperately not to do – it was like being thrown back in time two years, before the Final Wave, before my life fell apart, before he was killed. 

The Grey's closeness unnerved me in the same way the cloud did. It felt wrong and portentous, an omen of bad times to come – of an oncoming storm I was walking towards, unable to stop even though I could see the thunderclouds rolling all around me, tumbling and growing, threatening to engulf me and swallow me whole.

He had to stay close to my side. Of course, he did. After all, what husband, estranged for so long and adrift in a nightmarish world without his wife, would keep his distance from the one person he had hoped to find? And what wife would seek to distance herself from him, or keep him at arm's length when she had lost all hope that she would ever see him again?

The pretence was killing me. Each step with him at my side like the cruellest torture.

A couple of times, as we moved stealthily from hiding place to hiding place, our hands had brushed briefly together. The first time had been like an electric shock, a static strike that had shot up my arm like wildfire and I'd jerked away, noting Jace's frown and cursing myself for being so quick to react. The second time, I'd bore it with gritted teeth, refusing to look at Tom even though I sensed his eyes on me, his scrutinising gaze waiting to see if I'd finally crack and give up our horrible, nasty little secret.

That's what this was. A horrible, nasty little secret and the closer we got to our base, the nastier it felt, like some awful parasitic worm clinging on to my insides, burying a little deeper the farther we travelled until I thought I might never be able to be free of it.

Today, the silence of the city was doing little to ease my paranoia about Tom's plan to find sanctuary from his own kind within our group. Everything was working out a little too well for him.

He'd met Lena and had earned her trust by saving her. He'd tortured Rico and handed him over to us on a bloodied plate. He'd been in the right place at the right time to intercept our mission at Lancaster House. He'd manipulated this whole situation so that he could force me to bring him back to our base. And now, the city felt complicit in its silence and in its lack of alien presence. Was this part of his plan too? Had the Greys plotted an easy escape back to the Tube station, just so Tom could infiltrate our group?

'Are you okay?' Tom said, his voice soft, his face too full of concern, as I shifted the heavy backpack I was carrying, laden up with loot from the secret cellar of Lancaster House. He went as if to help me, reaching out to touch the strap which was burning a valley into my shoulder blade and I pulled away.

'I've got this,' I hissed, ensuring that Jace and Lena were far enough out of earshot.

We rounded the corner, taking shelter in between the shell of the Economist newsstand and a London sightseeing bus which now lay on its side, its once-glossy burgundy paint now dulled with ash and a thick layer of pigeon-droppings. Jace and Lena were already at a vantage point on the opposite side of Piccadilly Road, concealed inside the entrance of the old M&S foodstore, its treasure long-since looted.

Crouched either side of the narrow hiding place, I was too aware of the Grey's close proximity, too aware of his eyes on my face. I swallowed, scanning the street, doing my best to keep my eyes fixed firmly on our surroundings. The silence of the city mocked me, issuing a silent challenge to those of us who dared to think we could walk its streets unharmed.

I watched, my heart in my mouth for too many reasons, as Jace and Lena crept through the front of the foodstore, threading their way through fallen display units.

Stop it. Stop looking at me.

My fingers squeezed around the pistol grip of the SA80 and I raised it up, using the scope to scan the buildings for any sign of movement.

'Evie...'

Don't. Please. Don't say my name.

I held my breath, releasing it slowly, desperate to calm my racing heart.

'Evie...'

'Why did you do it?' I said, my head jerking so sharply towards him that he flinched at the sudden movement. 'Why did you kill that thing?'

His back was pushed straight against the newsstand, a tense awkward position that was so unlike Tom. Tom was always so relaxed, so easy in his posture and in the way in which he carried himself. The Grey's eyes flickered with uncertainty, his brow crinkling with confusion.

'It was going to kill you.'

He said it so matter-of-fact, almost as if he were talking to a child that clearly didn't understand.

'Why? Why was it going to kill me?' I adjusted my grip on the assault rifle, glancing over to see Jace dip out of view inside the store. 'It could have targeted anyone. Jace was the biggest threat in that moment. He was the one ready to shoot. Why me and not him?'

'You would have preferred it if it had gone for Jace?'

I spat a curse. 'You know that's not what I meant.'

Jace and Lena were out of sight. We had to move. Keeping as low to the ground as I could, I shifted around the end of the fallen bus and darted across the road, skirting past a tangled heap of bicycles and one bloodied and dented bicycle helmet that lay next to them. Reaching the front of the foodstore, I ducked inside the entrance, my boots crunching on the welcome mat of broken glass from the shop window. On the far side of the store, Jace and Lena were already at the other door which led out onto Stratton Street. Seeing we were at the vantage point, Jace nodded and slipped out of the doorway, his SA80 poised and ready as he eyed the windows of the tall sandy-coloured building opposite.

As soon as Jace and Lena were gone again, I turned back to Tom, who was still looking at me, only now there was less uncertainty in his eyes. A thin sheen of perspiration at the base of his throat glinted in the sunlight that was bathing the entrance of the store. Instantly, I was hit with an image of me kissing him right there, his hands hot on my back, our bodies damp and exhausted. God, how I hated these memories now, these little torturous melodies that seemed intent on gripping my heart and crushing it just when I needed to stay strong.

'Something passed between you,' I said, firmly. 'I'm not stupid. I saw it. It knew what you really were. Then, all of a sudden, it was looking at me. Like it knew me. What did you tell it to do? Did you give the instruction, is that it? Some weird telepathic exchange, telling it to attack me and not the others?'

'Why would I do that?'

'I don't know. Maybe so you could swoop in and save me? Act like the hero husband? Manipulate everything so that Jace would trust you?'

Tom stared steadily; his gaze unwavering.

'I never instructed it to attack you.'

'But something did pass between you? You were communicating.'

When he didn't answer, I turned the aim of my gun on him, pointing it directly at his throat. I remembered how his skin felt under my lips. Remembered the taste of him on my tongue. My finger hovered over the trigger.

The Grey swallowed. 'You're not going to shoot me.'

'I've shot you in my head one hundred times already. Each time, it just makes the urge stronger. You might look like him, but don't be so foolish to think that would stop me from putting a bullet in your throat. You've manipulated them, but you can't manipulate me because I know what you really are.'

'And what's that?' he said, raising a brow, coldness hardening his features. 'Your enemy? The one that killed your husband, and who then specifically and intentionally sought you out two years down the line because your group is the only one worth infiltrating, even though there are so many other worthless human survivors left to kill? Your people mean nothing to the hardline core of my species. One human is as insignificant as the other.'

'Then why not seek sanctuary - if that's what you really want - with one of those other insignificant, worthless humans? If, as individuals, we all mean so little to you?'

He slicked his tongue across his bottom lip. 'Because you're my best chance of survival.'

'Even though I'm the one pointing a gun at you?' I said. 'Even though you'd have it so much easier infiltrating a group where they all think you're as human as they are?'

'In another group, I wouldn't have you to back me up. I'd be alone. I'd be under suspicion. How long do you think it will be before other groups realise they might have already been infiltrated? Newcomers won't stand a chance.'

The silence crept in between us, curling around our legs, pushing its way between our bodies.

'It did know what I was,' Tom conceded finally. 'You're right. We always know, just as we know if one of our kind has disconnected from the central hive. What you saw was the skrycha reading me, connecting with what it could see in here.'

He tapped at his forehead. 'And in here, it saw you.'

I blinked. 'What does that mean?'

Tom dropped his arms, his gun hanging listlessly at his side. He was defenceless. Exposed.

'It could see what you meant to...' He paused, swallowed again. 'To Tom. It identified the connection between us. It targeted you because of me. I'm sorry.'

I stared at him, aware of the seconds ticking by. Aware that we should have moved by now and followed Jace and Lena, and yet we were here, standing where the sunlight could glisten on his damn throat while I tried to make sense of all of this.

With a shake of my head, I lowered my rifle and walked away, heading towards the exit at the side.

'Evie...' The Grey said persistently behind me. 'Evie, I said I'm sorry.'

God, he was either the best actor to ever walk this Earth or the most pathetic character.

'Eve... please.'

I turned on him abruptly, pushing the barrel end of the gun up into his throat.

His damn throat.

He froze, panic flickering across his face.

Tom's face. 

'Stop it,' I hissed. 'Stop calling me Eve. Stop saying my name. Stop talking to me. And stop saying you're fucking sorry. You're not sorry for anything. You're not. If you were, you wouldn't be here now. You wouldn't be torturing me like this. For the record, I don't believe a word that comes out of your mouth so stop trying to convince me. I don't believe that thing attacked me because of some memory that still lingers in Tom's head. It did attack me because of you but only because you told it to do it. Because you're manipulating everything and everyone to suit your needs.'

I pressed the gun a little harder against his skin, enjoying the way he flinched away from it.

'Now, I'm doing this because I have no choice, you've made sure of that,' I said. 'But trust me when I say, that if at any moment I think you're a danger to anyone in my group, I will put a bullet through your throat or anywhere else I choose to. There is no connection between us, got that?'

I pulled away, backing up a little, seeing the dark glint in his eyes and feeling not scared, but justified, vindicated that I could see the Grey in him, because it made this so much easier. Identifying him for what he really was, and not for the flesh he wore, meant I could hold on to that, use it, wind myself around it and push back at all his tricks and manipulation.

Shooting him a look of utter derision, I slipped out of the foodstore, being sure to keep my guard up and scan the area as I moved stealthily and quickly to the Stratton Street entrance to Green Park station. Jace and Lena were waiting inside, just on the other side of barriers.

Jace scowled when I reached them, with Tom not far behind me.

'You took your bloody time,' he said, gruffly. He'd been worried, of course he had. I cursed myself for making him wait. This wasn't like me. I moved with him. I was consistently reliable when it came to being topside. He could count on me and I'd made him feel like he couldn't.

'Sorry,' I said, swearing to myself then and there that I would gain control again. I wasn't going to let the Grey win. This was my group, my friends, my family and he wasn't going to be a part of that.

'Don't be mad, Jace,' Lena said, looking pointedly at me. 'I'm sure they just wanted some alone time to catch up.'

Was there something there in her eyes? A glint of something other, a hint of knowing? She glanced at Tom by my side, a small smile on her lips and all at once I was thrown back into thinking I wasn't just taking one Grey back to the base, but two. I looked to Tom, but his face was unreadable, if not a little flushed.

Jace raised a brow, clearly unimpressed. 'Fucks sake, you can save that for later. We still have a long journey ahead of us.'

It was my turn to flush now. I felt the heat creeping into my cheeks, unwanted and unwarranted. Fuck you, Lena. The Norwegian grinned at me as Jace walked away and I was gripped with a sudden fear as I watched them both navigate the frozen escalator down into the darkness, both turning on the torch light on their rifles. I could still see the dull glow of the beams of light as they disappeared from view and my stomach lurched at the thought of heading into the tunnels.

Was this where they would strike? Would we walk into the darkness wondering what horrors lay ahead, only to hear the chilling click-click-click of the Greys at our side?

I swung the SA80 onto my back and went to jump the barrier.

A hand encircled my wrist and for one moment, I was sure when I looked down, I would see the long, thin fingers of the Grey gripping my arm. The faintly oily residue of its skin on mine.

I looked. Tom's hand. His left hand. I faltered at the sight of the wedding band still on his ring finger, scratched and slightly tarnished, but still there.

He was so close now, that I could smell his skin. His hair. See the crackles of grey that ran through the striking blue of his eyes.

'You're a liar,' he whispered. 'You're not going to do anything.'

Oh, there you are. The Grey. The Grey. The Grey.

'You already think I'm a danger to you and everyone in your group. You don't believe me. You don't trust me. And yet you still haven't killed me.'

He smiled then and it made me think of DI Eddie McCain's smile in the interview room. It was a predatory smile, fashioned with Tom's mouth, but a smile that made my breath catch in my throat and my heart thump hard in my chest.

'Why do you think that might be, Evie?'

His thumb skimmed over the skin on the underside of my wrist. It was a barely-there touch. So small, so soft and yet I jolted, a small gasp exhaling from my lips.

With a low chuckle, he let me go and deftly jumped the adjacent barrier.

I watched as he walked away towards the escalator. Tom's walk. Tom's back. Tom's posture.

Tom. Tom. Tom.

With a sinking feeling in my stomach, that probably burrowed deeper than the tunnels under London, I slipped over the barrier. My legs felt weak. The injury to my head seemed to take on an angry pulse, reminding me of its presence and prompting a surge of nausea to rise in my throat.

Reaching the top of the escalator, I clicked on the torch on my SA80, took one last look back at the sunshine basking Stratton Street in summer city heat, and then I did the only thing that I could.

I followed the monster down into the dark.