'Do you know what I learned to love most about the New World?' Abby said, next to me, as we pressed our backs up against a column of the Queen Elizabeth II Centre, just across from Central Hall.

Her ash-blonde hair was tied back from her face, making her seem younger than her years, but today, a note of exhaustion hung on her features, a weariness I hadn't seen on my friend's face in a long time.

'I know it seems weird to talk of loving this place, but when they came and we were getting killed or in hiding, I loved that there was no building in London I couldn't get into. Didn't have to put up with people sneering at me, spitting on me or worse, treating me like I was invisible. Didn't have to walk past all these posh buildings and wish I could wander inside just to keep warm or to get off the streets for a while and forget what I was. I could go anywhere I bloody well liked. I always wanted to go in there.' She nodded towards Central Hall. 'Not so much now, got to be honest.'

I glanced at her face. A flicker of trepidation tugged on the corners of her mouth. She was scared. We all were.

'I know what you mean,' I whispered.

She chuckled, but not unkindly. Abby was never really unkind. Being homeless might have done many things to her, but it had never made her cruel. 'You? Miss Art Historian herself who lived in art galleries and museums? What would you know about it?'

'Well, it's just after...' I paused. After Tom had died. That's what I'd been about to say. I swallowed it down, buried it, buried him, and smiled. 'I just remember a time when I didn't feel welcome. Not so much in buildings like that, just with certain people. Family. Friends. People I'd known for years. It's a horrible feeling, suddenly being an outsider.'

Abby stared at me and for a moment, I thought she'd laugh at me for even daring to compare whatever I had felt to her situation or tell me I was a self-centred idiot who knew fuck all what it was to be an outsider. Instead, her gaze displayed only warmth.

'Do you know something?' she said. 'I think that's the closest you've ever gotten to opening up to me, without really telling me anything at all. Maybe you're not such a cold fish, after all.'

'You think I'm a cold fish?'

She shrugged. 'Okay, lukewarm, maybe.' She grinned, nudging me with her elbow.

'Come on,' I said, tightening my grip on my rifle, doing my best not to look up. 'Let's get this over and done with.'

I never thought I'd crave the silent and still graveyard that was now the rest of London, but I did. I wanted this done with. I wanted to be back there and out of this place.

The term, Black Zone, was fitting, not only because of the wall of dark cloud that surrounded it, but because of the lack of light within it. The alien craft that sat above Westminster and Buckingham Palace blocked out much of the light, plunging the city beneath it into a permanent, eerie dusk. It was cold here, as if the Greys had leeched the warmth from the Earth, a stark contrast to the suffocating tunnels and the sticky heat of the city outside.

Up above us, the craft hung in the air, so vast, so monstrously mammoth that it seemed to defy every possible law of engineering as to how it could get off the ground in the first place, let alone remain still and unmoving in the skies. It seemed so close to the tops of some of the buildings, that I was sure that you could reach a hand out of a window and touch it, not that I would have ever wanted to. There was something about the structure of the craft that I found deeply sickening.

From here, the entire base seemed to be made of a mass of black stalactite formations of varied shapes and sizes. There appeared to be no uniformity to it, and although I was certain it must be a metal of some kind, it had the appearance of slick, oil-drenched rock and it was that slickness which nauseated me to the core, because it reminded me of their skin – smooth and yet with a greasy sheen to it that turned my stomach. If I hadn't known it was one of their ships, I might, at first glance, thought it to be some kind of mutated cellular being, a monster with slick flesh, breathing in and out above us.

I turned my thoughts away from the possibility that the craft could sense us down here and was waiting to reach down and absorb us into its flesh, and focused on the building ahead, which appeared only slightly less ominous than the ship.

Checking that the area was clear, I darted forwards, skirting along the edge of the building, past the blown-out windows, treading carefully so not to crunch down on any shattered glass. Across the street, the lawn area was now bomb-scarred, and I could see Tom with Jace and Gav, moving covertly through the mass of twisted, burnt trees that had been felled during the war. Behind them, I could see Levi and Taj, Lena and the others moving past the ruins of Westminster Abbey, the gothic towers all but destroyed, leaving barely a charred skeleton behind.

The plan was for one group to take the right-hand side, the other, the left, both avoiding the main entrances on the curved front of the building, where the elobrately carved baroque-style stone angels looked down upon all those who would dare to enter. Once inside, a small group would venture down to the basement to set the round of explosives we'd stolen from the raid on the Saudi Embassy, leaving the rest of us to head up to the Grand Hall to free however many captives were held there before the timers went off.

Moving deftly towards the nearest corner of the Queen Elizabeth II building, I glanced over to see Tom staring in my direction, his eyes wide. He appeared frantic, and next to him, Jace and Gav had frozen still, pressing themselves into the fallen trees as best they could. Something was horribly wrong. Even from here, I could sense it. With one quick motion of his hand, Tom pointed somewhere out of our line of sight and gestured for us to stop and go low, and I abruptly pulled Abby down behind the wall, just in time to spot a Grey appear from the direction of Storey's Gate.

With our backs pushed into the wall, crouched tight into our hiding space, I had no idea where the Grey had gone or how close it was to where we were concealed. From here, we couldn't see a damn thing. Inside my chest, my heart was beating hard and I clamped my mouth shut to suppress the shallow breaths I knew were bursting to break free.

When I heard the click-click-clicking of its throat and the low, strange cat-like purr that came with it, I knew it was close – too close. Altering my grip on the rifle slowly, carefully, I prepared for the inevitable shot, knowing that we were probably going to have to engage, no doubt throwing the whole mission into jeopardy if we did. Where one Grey wandered, there was always more of them close behind and we had been stupid to think we could make it this far without encountering any on our journey. As if my thoughts had given rise to reality, there came the unmistakable sound of another Grey answering the first, it's throat-click a little farther away.

The wait was agonising.

Seconds stretched. Tension thinned out to the narrowest of threads. And the incessant pounding of my heart just kept going.

Thump-thump-thump.

A shrill, chittering noise intensified, echoing through the air and the dull clap of steps on the ground – too many steps to be just two Greys.

Fuck. This was a squadron. It had to be.

We remained frozen in place, keeping as still as we could, yet poised, ready – and yet not ready – to strike, to take a final stand if need be. God, I wished I could look and just know. The not-knowing was the worst and the urge to take one tiny peek was overhwleming, but I stayed where I was, tuning in to the sounds, focusing solely on each step, each click, each high-pitched insectoid shriek.

After a while, the sounds seemed to grow fainter, fainter, fading into the distance, but I knew too well the dangers of poking my head up above the parapet too soon. The key was patience – always patience.

I turned my head slightly to look at Abby, who did the same, our eyes locking together in silent agreement. She nodded and carefully, I shifted position so that I could peer over the wall.

On the far side of the square, a now-dulled yellow coach stood blocking half the entrance to Great Smith Street and I watched, wide-eyed, as a Grey deftly climbed up the side, it's long, lithe limbs easily helping it reach the top where it skittered across, jumping down the other side and disappearing from view. Steadily, I scanned Storey's Gate, seeing no more signs of any Greys coming our way, my gaze coming to rest on Tom, who's face was so pale, it was like seeing a ghost looking back at me from across the square.

'Shit, that was close.' Abby exhaled through her teeth, turning to face in the direction of Central Hall.

'Yeah,' I said, trying to roll the tension out of my shoulders and failing miserably. 'Too bloody close.'

Glancing behind, I could see a few from Levi's group, including Mali, waiting at their position by the column, where Abby and I had been just minutes before. Over on the lawn, Jace crept out from behind the dead tree and darted across to the steps, concealing himself behind the small wall just across the street from the main entrance. Soon, Gav and Tom followed suit, with Taj, Levi and the others advancing more slowly from the opposite side, ensuring the Greys had gone before they moved forwards once more.

Finally, with a gesture for us all to proceed, Jace, Tom and Gav moved out from their place on the steps and ran quickly and carefully across the street, down the side of the building. Once they reached there, Abby and I crept up over the wall and followed them. Goosebumps raged over my skin as I ran, my gaze darting left and right, feeling the presence of the craft above my head as if it was pressing down upon me the closer I got.

Down the side street, Tom was waiting to help hoist us up onto the roof of the café located on the lower ground floor. One of the glass panels was missing, and one by one, we lowered ourselves into the café below, dropping into the gloom. With the glass roof, the café had always been a bright and airy place to grab a quick coffee, but not now. Now, it was crammed full of shadow. Still too exposed, we daren't switch on our torches yet, but as my eyes adjusted to the dark, I spotted movement on the counter top and resisted the urge to pull my trigger, realising it was just a rat, albeit a pretty large beast, its eyes glinting in what little light there was. As with most food places in the New World, the smell of rotting food and gone-off milk still hung in the air, even though the rats had clearly had their run of the place and feasted on what they could.

Wrinkling my nose in disgust, I headed to the door where Jace was stood, inching it open a crack to ensure the coast was clear before we moved on. I hesitated momentarily to ensure that Tom had made it through into the café, before quickly following Jace out into the lower ground foyer, heading towards the front staircase.

There were three floors to ascend, scanning each one for Grey presence, before we reached the Great Hall, where Tom said they were holding the humans they'd harvested for whatever foul purpose they had planned. Three floors to cover before the timers went off. Three floors of potential danger behind every door, down every dark corridor.

Gritting my teeth and doing my best to move as quietly as I possibly could, I made it up to the ground floor and the main reception area. The ground floor was the easiest and quickest to search, with just one small meeting room to check, which proved, thankfully, to be empty and soon, we were heading up the stairs again, this time to the first floor.

With Taj and Levi's group concentrating on the smaller meeting rooms at the back, we focused on the much larger, opulent library and lecture hall at the front, that took up most of the space on the floor. Despite the huge windows, the dim light outside meant any light inside was a luxury, but it was evident almost upon entry that both rooms were devoid of life. With their high ceilings, and vast empty space, the rooms gave off a ghostly aura that sent shivers down my spine. I didn't like the emptiness. The deathly quiet. The hugeness of the place that should have contained at least some signs of life, even if those signs of life were alien.

Instead, the vacuum of silence screamed back at us. Cold. Lifeless. Dust particles hung in the air, undisturbed, as if they had been frozen in time.

Retreating back into the reception area, the same unease I had felt when confronted by the black wall of cloud resurfaced, crept along my shoulder blades, making my neck muscles stiffen and my back itch with perspiration.

I'd expected to have come across some Greys by now, Hell, maybe a whole bloody army of them, but the place seemed almost deserted. My skin prickled uncomfortably and visions of walking into the Great Hall to find it had become one giant morgue filled my head. What if we were too late? What if they were dead already and this whole thing had been a dangerous, foolhardy mission doomed only to end up fruitless, faced with thousands of corpses? I shook off the icy thought, convincing myself that we'd smell them by now if they were dead, but also thinking back to what the Grey had left behind of Tom when he'd taken him. Is that what waited for us above? Human residue hanging in the air like dust particles?

'I don't like this,' Mali whispered aside to her companion, vocalising exactly what I was feeling. Her long, dark hair was pulled back into a bun, and like me, she wasn't wearing a jacket. Her forearms glistened with a sheen of sweat, despite the chill of the building. Her companion, an older guy, possibly in his late-forties, nodded his agreement and they both glanced at me, before looking away quickly as if they needed to hide their concerns from me. I wanted to tell them I agreed, that I felt it too, but before I could open my mouth, a hiss emanated from the end of the corridor and a sudden flash of movement in the shadows above had us all aiming our weapons upwards, as a Grey scuttled unfeasibly fast across the ceiling.

Behind it, clearly in pursuit, Taj, Levi and the others ran towards us.

'Found it in the back stairwell,' Taj said, as he drew close, his handgun trained on the creature, his breath coming in rasps. Blood was trickling down the side of his face. 'Fucking thing jumped at me before I could do anything.'

Realising the numbers that it faced, the alien crossed the room, keeping to the edges of the ceiling and eventually backing itself into a corner, where it pulled back on its long, spindly legs and hissed at us again, its eyes glinting maleovently like the vantablack cloud that surrounded this part of the city.

'Careful, people,' Tom warned, keeping his voice low and calm as possible. 'Take a shot and we could bring a whole army in here before we're ready.'

He was right. We all knew the plan. We had to get in and up to the Great Hall with as little noise as possible. Silence and timing were key to the whole mission. Once we were there, we could fire as many rounds as we needed to, because we knew the explosives would detonate right after and by then, it wouldn't matter if the Hive had awoken to our presence, because we'd already have hit them hard and made our first stand against them. We couldn't afford to risk making any shots unless we really needed to at this point.

Rocking back and forth slowly on its long limbs, the Grey surveyed us all with pure malice, its large black eyes drinking us all in, its mouth a dark, gaping slash across the bttom half of its misshapen head.

We needed it down from the ceiling and fast if we were to get to the next floor before the explosives detonated.

Levi began to circle to the left, moving closer to creature, which shrank back, like a spider seeking shelter in the darkest corner of the room. His eyes flickered to me briefly as he passed, and in a whisper, he said, 'Still got those knife skills, Evie, my girl?'

I stared at him, instinctively sensing what he was planning. Painfully slowly, I shifted my rifle onto my back, as the creature kept its intense gaze fixed upon the huge human that was getting closer and closer. It hissed again, the sound long and drawn out, snaking through the room and tugging on my nerves.

'What the fuck, Levi?' Tom said, about to step forward, halted only by Levi holding out one hand in a warding-off gesture.

'It's all good, Mr. Morgan. We got this. In fact, everyone take a step back, if you will.' Nearer and nearer he got, the gap between him and everyone else widening and all the time, he never took his eyes off the Grey and the Grey didn't take its eyes off him.

Opening its mouth wide, it tensed, that horrible clicking rasping from the back of its throat.

'That's right,' Levi said, his usual low rumble sounding strangely coaxing. 'Come on, it's me you want. Get down here and do your thing. I'm all yours, my grey friend. Every little bit of me.'

Finally, he stopped, and swinging his rifle onto his back, he dropped his hands to his side, defenceless.

Without a sound, the creature sprang off the ceiling with such power, using its legs to propel it forwards, hitting Levi with such force that it knocked the big man off his feet and together they went tumbling to the floor, a mass of muscle and limbs, tangled together as they rolled across the room.

'No, wait!' said Taj, holding out his hands to stop everyone from taking aim, in fear they'd hit Levi, who continued to grapple with the creature, ending up on his back, with the Grey above him.

I knew then why Levi had offered himself up as bait. I'd been on the receiving end of an airborne attack and knew just how strong and agile the Greys could be once they got you down onto the ground. Fending them off was no mean feat, and yet Levi was doing a pretty good job of holding it at bay, despite the grunts of effort he was making to defend himself.

Withdrawing my blade from its sheath, I jumped onto the Grey's back, ignoring the feel of its slick skin beneath my hands. With a grunt of my own, I quickly plunging the knife into the back of its neck, not stopping when I felt the wet, thick resistance of flesh, not stopping until it pierced through to the other side, not stopping until its body finally went limp and its dark blood gushed freely over Levi's chest onto the plush carpet underneath.

Sliding off its back, I felt strong hands steady me, a familiar warmth enveloping me as Tom pulled me against him. 'Christ, Evie,' he whispered, as Levi pushed the now-lifeless body of the Grey off him.

Footsteps rapped sharply down the corridor, and as one we all tensed, raising our weapons at whatever was now coming our way. Even Levi, still on the floor, had grabbed his handgun and was pointing it at the figure that came rushing through into the foyer.

Coming to an abrupt halt, Lena stood with her hands raised, her rifle held aloft in the air. Her long, blonde fringe was stuck to her forehead and a dark stain plastered the front of her shirt. Her face, pale and shiny with sweat, was stricken with panic.

'We have to get moving,' she said, her chest heaving in an out as if breathing pained her. 'They're in the basement, they're coming. It won't be long before the rest get here.'

'Where are the others?' Levi said, climbing to his feet.

'I don't know,' she said, shaking her head. 'Seb didn't make it, the others were behind me, I don't know what happened. We have to go now! The explosives... we don't have much time!'

'Okay, you heard her, let's go,' said Taj, turning and moving towards the Grand Staircase behind us, but as we began to follow, the sound of Levi's voice resounded and, to my horror, the unmistakable click of safety catches being released one by one behind us.

'I don't think so, Taj, my man.'

We turned, almost as one.

Levi's people stood, gathered together, their weapons all trained on us, their eyes full of hatred and anger. All signs of our uneasy truce had been eradicated and all I could see now was suspicion. It rolled off them all in great, tumultuous waves.

Levi stepped forward, his handgun raised, pointing it directly at Taj.

'I'm sorry, my friend, but you aren't going anywhere.'