Thinking back Scott couldn't remember quite how he'd ended up finding himself behind Schofield by the same double door as the one Amy burst through. He remembered the slosh of all that water from the sprinkler system which by now made no difference to his trainers and just ran down his socks. The back of his legs was wet from where he'd fallen. The double doors to the lab and everything else in his vision was dominated by the wide-set frame of Schofield thumbing the Return key as if deliberating to put it in. The key was nothing special, regular teeth in a single sheet of steel, six grooves in total that from here looked like they couldn't break skin no matter how Schofield gripped it. The key went into the lock, and Schofield turned it.

Scott felt for the grip of the revolver. It was empty, but it was his for now. The fat man could have more than one weapon. Scott reckoned Schofield wouldn't have given up this one so easily if he'd only had the one. Surely he must have a spare, and any minute he'd bark the word and bend down to pull it from his ankle like in an old Western. Scott held the weight of it in his jacket pocket and felt he shouldn't disturb it. It was unloaded, but he could still sense it pointed muzzle downwards to his thigh. It was a gun which had been used to terrorize them if Amy's story of the hospital was to be believed. It felt tainted. Scott had seen Amy step through the Return door from the far end of the corridor. He'd gone to tell Raynes they'd found a key, and to grab April so they could get out of here. Now he didn't know what to think. It disturbed him seeing her like that, one moment walking through the door one direction, and returning through it faster than was possible, quicker than it would take someone to spin on their heel and step back out again. And coming out of that door was what seemed like a different person. There was no calm, composed, sarcastic Amy.

Schofield clicked open the door to the lab server room and pulled, but when he did the door got heavy and wouldn't budge. He braced his feet against the threshold, pulled harder, and it opened a crack. His grip faltered on the handle as the hinges protested. It was too slippery. He pulled with both arms, but there wasn't any of the purple calm light of Otter's world seeping out from under the threshold when he looked down. "It won't open, I don't kno-", his grip slipped as the door sprung back to slam itself closed, and went through with velocity in the wrong direction against the hinges to splinter them loose at the frame. The door stayed there, swinging open the wrong way. It was the only anomalous object left in the place the door opened to. There was nothing beyond the door. Not just nothing, but Nothing itself. The door of the lab fell away into doomed emptiness. Light fell through the Return door and the gaping chasm pulled at the world on this side with a force that threatened to rip out the doors and the frame of the portal itself. Matter crumbled and was atomized into an accelerating mist at close to the speed of light through the void of space. There were no stars in the world beyond the return door. The stars had been blown apart by more and more inconsistencies in the laws of physics on that that side some hours ago. There was no London, Hyde Park, or anything at all beyond that Return door. There was no Otter, no fuchsia-dead city of Vern-Delnitz where time slows to a crawl. No, those had been the world Amy had last been in. For Raynes and Schofield the return was to the Brompton oratory, or where it stood before it too was atomized. It was a return to the world where it was a mess of orthodontics and nastiness, a world where the three of them except Amy had been caught, where Matt hadn't been controlled. Beyond the doorway time had lost all meaning. The world beyond had been obliterated, and nothing remained testament to there being anything there at all. Only the door, strained as far as the hinges could go and illuminated in sharp angles still existed in the universe beyond the doorway, and where the light didn't strike it disappeared into a black sharp void. The door was paired to nothing at all. No doors existed in that world, and so the key just chose a place in that Returned world that had once been the vestry of the Brompton Oratory. Scott watched as the screws holding the hinges in place struggled, whined and then as they were ripped out in small, heaving increments. The doorway strained and the portal held under the atmospheric pressure that threatened to break it open and suck away the air and everything else on this side as well. That side of the door would have no more Aprils.

"Agh!" Schofield fell backwards. He was off-balance and landed in the water. His shoe grazed through the threshold and atomized the heel of his bad leg. He screamed as the threshold atomized it also to the bone.

"Rowenstein! For fuck's sake," Schofield gasped and scrambled back from the door on hands and knees. "Hale! Help me up!" There was the office, and the water around it seeped and gushed in deep red. And Schofield screamed to close the door and strained with help to get up. "Get some cord, cable, anything to pull it shut. Close the fucking door, close it, close it now."

"Matt, take him. Drag him away." Scott looked to the broken computer room, and left his friend to help Schofield trying to stem the bleeding with his polka-dot cloth. It had instantly seeped a deep crimson. Schofield howled. He motioned to Raynes then, and waved desperately. "Raynes, come here! I can't close it. Come on, help me. For God's sake help me and close it! Leave Packard! Just come here."

Scott found a wired mouse that ripped free and burned him with friction when he pulled. Stay calm. Scott dropped the wire through the door and found that throwing something through the doorway just made it disappear into nothing. The wire was cut clean. The key and the door were there, in the blackness out of reach, but anything else that fell through got deleted.

"It won't close," shouted Scott. They came running then. All of them except April. And when Scott tried to pull the door shut with a steel bar it went through and flew out of his hands into the black void. The pull was too much.

"We can't close it. It – it won't do it. Amy, what did you do? Did you go through that? Tell us," screamed Scott. Raynes tried his best to bandage the huge man and ripped giant swathes of cloth from the lining of his jacket.

Amy stared. She couldn't understand it. "N-no. No, it should be a square, medieval. There should be a fountain. And an otter. And, and-"

"Aims, can we close it? Is it possible."

"No. You can't. But it's just a return key. I don't understand. I don't know why-"

"I thought it was meant to be 'enter'?" said Raynes.

"No, this is 'return'."

"If we can't close it, there's no point wasting our time," said Raynes.

The hinges creaked from the force of the blackness and the frame started to splinter. And it was then, when the sirens of fire-trucks weren't far off that April joined, half-walking and half-crawling when she had to, and saw that through the door was nothing but the black waves, that it was a place of Aprils long lost and dead.

"Apes take it easy. You were out for ages. I'm sorry, I would've come back."

April tried her best to stop the vision swimming. She tried to stay in May, stay in control. Don't go back, ignore the monoliths. The monoliths were there, all gleaming ghost-like, superimposed on May through the corridor and cutting straight through the floor, the wall and part of the ceiling. She ignored them, tried to focus her eyes but realized she didn't have her glasses. The main points. Just the main points. Say them, tell them what you've found in those libraries where there's never any dust. Tell her.

"It's under Hyde Park," the words struggled out it single syllables. She toppled, and held on to Aims for support. The floor was wet. She looked down and saw Amy and Matt above her.

"What's under Hyde Park? April, tell me. If you can help us then please, tell me."

"Lana," heaved April. She was bleeding. Her face stung from being hit. "Peregrine." Lana Peregrine was one of many on the Atomic Vice team. April had seen the entire timetable planned for next month's experiments, had lived through the experiments in April. She knew today was Dr Peregrine's time slot on the machine. "Blackett building. Sixth Floor. Make her take you. Make her take you to the Atomic Vice. That's where it all started."

"Matt, Scott, help me sit her up. Forget the door."

"What about the water. The floor's soaking wet."

"Shut up and help," she replied.

"No," said April. "Listen," she pointed to Matt, her tongue struggled "the maintenance report. Make him do it. The S552 maintenance report. Every month they make one. I've had time, more time than anyone to find the right words. Do it. Those are the right words."

"What? April? April, wake up. What maintenance report?" She shifted April's weight, and tried not to slip. She looked to Schofield struggling to get up. His foot was bandaged, face gritted into thin gasps. The word revenge came and went through her mind, and left her feeling unsure. The door they'd opened was pure blackness. Maybe this was a little like what deconstruct-reconstruct portals did to people.

"Find her," April heaved. "Sixth floor. Office. Dr Peregrine. On the calendar." April gripped her shirt.

"On the calendar?"

April nodded. "She should've been on today." She struggled to force the monoliths away, both the ones here and their parallels through the black door. She struggled to push the waves down where they belonged. For a little while she succeeded. "It's a dead wonderland. The door. It's where you came from."

"The door? But no, when I went through there was Otter, and everything was fine."

"Not that one. The world you lived in. It'll never have Aprils again. That's what it looks like now. That's what we're up against."

***

They had to take the walkway linking the Maths building with Physics. They occasionally passed someone and ignored their shock. It was a slow process. Raynes had to carry April and Schofield had been forced to hold on white-knuckled to railings, doors, anything and everything in reach. They'd emerged after a long walk from a side-door on the first floor of the high lobby of the Blackett Physics building. Schofield could sum up the gigantic decaying 60's monument to physics as distinctly retrofitted. Parts of the ceiling were damp, the halogen lights were all different colours seemingly at random and had presumably all once been a single shade some time ago in the unknown depths of the past. The semi-circular bunker of a reception desk at the far end of the ground floor below he'd have bet even at this distance was out of reconstituted wood veneer. Thankfully it was empty.

Between thoughts of swearing and hissing at the pain it came to him that the shine of the place was what set it apart as distinctly worn and aged. The lobby tables reflected back their perfectly smooth veneer. The marble floors were spotless, and felt out of place. There was no purchase on the walls either – they were marble too. There'd been a plaque of dark marble with its gold lettering that commemorated the building's grand opening by the Right Honourable someone. BLACKETT BUILDING. There were elevators close by, and when he waited for them he couldn't escape the irony of being almost unconscious at a place that was not quite but so very close to being called 'blackout'. Well it fit the theme of the day, he thought bitterly, and he survived by counting the seconds until the lift arrived.

"Did she say anything else?" asked Raynes.

"That's it. Find this Dr Peregrine, find the Atomic Vice," said Amy.

"You're sure she's here?"

"April thought so."

"No matter what we don't have long now," said Schofield. "We need that enter key. The next time it has to work, and I don't care where it goes as long as it's not here."

He entered the elevator and someone slammed the button for sixth floor as requested by the girl who had the visions. It was doomed. Schofield thumbed the 'Escape Key'. It had been their last-ditch option, and had been discussed with Raynes as such. Reset it all, go to a place that was like here but not quite, and retry this whole charade in a timeline that wasn't doomed. But the doors weren't safe and he was injured, and he'd come out the other side injured too if they used it. What he didn't know was that it wouldn't work. Not all timelines are doomed.

He barely remembered the rest of the journey and now he found he stood in front of a solid door to an office with dark, sticky wood that fit the rest of the heavy-set aesthetic, and a hard blue plastic replaceable placard mounted that stated they were in the right place – 615 LANA PEREGRINE. When Schofield knocked it left streaks. He'd been careful to leave none on the floor but you could only do so much, this time blood was the least of their issues. They heard someone on the other side roll back a chair, and then say 'come in'. Maths may've been evacuated. Thankfully Physics had not.

"Go on, Packard. Open it. You're from Maths, so next in line after April." They'd taken April's card off her and used it for the doors. She was slumped, breathing heavily and forcing away monoliths and darkness on all sides. Packard opened the door.

The office beyond was riddled with folders and unknown knick-knacks of all sizes. Stacks of papers overflowed in heaps of uncategorized administration that were kept as far away as possible from the main rolodex and the piles of pens taken from a dozen conferences. Schofield saw the edges of dozens of post-it notes poking beyond the confines of her computer screen that arranged themselves from this angle like multi-coloured scales. Planters on the windowsills overflowed with ferns and shrubbery and complemented the hard-backed folders in the inbuilt shelving units next door. The carpet was a barcoded shade of grey. Seemingly overwhelmed by it all sat a thin woman, confused.

"Can I help you? Excuse me? Oh God. What happened to you?"

"Are you Doctor Peregrine?" asked Amy.

"Yes. Who are you? What happened to you? You're all wet, are you Jane? Our personal tutorial isn't until Wednesday, and sir, you-, what are you-"

"So you've noticed" cut in Schofield "I'm bleeding. Sorry about staining your door." Schofield limped into the room and sat himself down heavily on a well-indented sofa. Dr Peregrine looked from one face to the next, picked up the phone and started to dial. Amy got to her fast enough to press the end-call tab. "Please. Stop. Dr. Peregrine, you have to help us," she said. "Our friend told us to come here."

"What are you doing? Listen, if you don't stop-" she pulled out a mobile "I- I'm calling the police. A-and the ambulance. How did you get in here? This is a restricted building."

"No. Wait. Please, listen," said Amy. "This is April, one of your students. I'm Amy. We're all first-years."

"What happened to you?"

"You're part of a research group that works with something called an Atomic Vice," said Amy.

"Excuse me?" Lana put down the phone. She stood up and backed away. The ferns brushed up against her and she felt for their cool leaves. She wondered if the planters could be used as weapons and remembered how much she'd struggled to pick up the weight of the huge variegated Mother-in-law's tongue. She'd over-watered it and the planter had leaked over the white ledge to spill dirt all over the carpet. "Wha- I, I don't understand. No, you must be mistaken."

Her throat was dry. The girl with the damp hair was trying to explain. There'd be no explanations. Lana struggled and rounded on Schofield. "Get out! All of you. Get out of my office. I'll have campus security up here." It didn't make sense. Wait, this wasn't the right course of action. She had to detain them, call the police. Campus security was the very minimum.

Schofield produced something from his pocket, and passed it to Scott across the unconscious April deposited sideways on the sofa. Scott then handed it to Raynes. The contents of the handkerchief found itself arming the door.

"Lana," said Schofield "shut up. Just listen."

"These are classified projects. You have no right-"

Schofield struggled to find the lanyard he was looking for. He held it up. "This is my identification. Here. My name is Schofield. I'm here on behalf of the secret service. This man here in the suit's one of the CIA's finest, Mr. Raynes. We are qualified to ask you about anything we damn well please."

Lana approached him, studied the lanyard. Was it real? What did a real secret service badge look like? Like this? It wasn't meant to look like a police badge? She couldn't remember seeing any like these in films. Surely they didn't just carry them around for anyone to identify them. Surely not. "I'm sorry, but I can't talk to you. I don't know you. You can request a meeting with the project lead."

"And who's that?" asked Schofield.

"James Marigold. But, you need a formal request, and approval, and-"

"Paul show her the door," said Schofield.

"Fine."

Lana tried to scream but nothing would come. Her lungs wouldn't work. She bent over double at the force of the blow that winded her. No. It couldn't end like this. No, please. She lashed out and tried to find purchase to scratch at Raynes. Someone else was shouting. It was the girl by her desk. Lana's legs were pulled from under her as her arm was wrenched off balance away from the middle of the room and dragged towards the door by the American. She coughed, tried to breathe and gripped him through his tattered suit. She couldn't move. Her kick connected with something. This is it. Holy God, I'm going to die. I've not had time. I've only just got this job and I don't know anything. I just work here. It was a mistake. They were mistaken. She hadn't done anything wrong. There was nothing wrong. She went face-first to the ground and the top part of her body was dragged and wrenched upwards, her hand crushed. It was the man in the suit who then forced her palm against the door. She screwed her eyes shut, still kicking and feeling the carpet burn her each time. He was out of range and the angle not right to hit him. "Stop! Raynes, you're hurting her-", said the girl. Then the pressure hit her. It seemed to crush her from all sides for a split moment, and then left. The voice of the damp brunette cut out mid-sentence.

Something shook the floor and reverberated. She looked up. The world was blurred. Everything ached, and spun. Her arms shook, she couldn't get up. A door far up the corridor opened.

It was her door, 615.

It tilted and struggled to stay vertical. She closed her eyes, and rested. She tried not to breathe too hard. Breathing came in nauseous sobs and each one was agony enough to start the next.

"Did it work?" asked the voice of the Englishman.

"Yeah, she's down there," replied her attacker. There was the sound of irregular footsteps. In a blur she saw them, most of them at least. The one in the suit was closest. Wait. Lana failed for a minute. It wasn't possible. Had she passed out? How long? No, she hadn't. She felt sick, and put up a hand. There was a fire alarm a few paces away. If only she could press it everyone would come out of their offices.

"You pieces of shit. How could you." said the one with the wet hair.

"We haven't got the time. She's the enemy. This is not up for debate," said the American.

"Don't hurt her, Raynes. You don't need to." Then other voices joined in, lower this time. It would be the boys.

Lana heaved. All of it felt as if happening to someone else, as if her head was attached to this view by rubber bands that flexed and bent with the tilting shine of the floor. She was crawling along it, struggling and finding almost no purchase. The fire alarm button wasn't getting closer. Beyond a pair of '60s-era swing-doors she saw the museum displays by the sixth floor elevators in their glass cabinets. And then the whole thing tilted so suddenly.

"Hey, Peregrine." Someone clicked their fingers. They were dark, splattered with blood. "You awake?"

"She's delirious," the voice was deep, American.

"Carry her back." said the first one quietly. She caught the fat man's gaze more clearly. She wished she hadn't.

"Yes that means you, Scott," said Schofield. "Grab her other arm. We have to carry her, same as April." Lana considered shouting for help. Why wasn't she screaming? Why? Because it wasn't possible, but if it was possible she didn't want the rest of this corridor to know. None of this could be real. And just like in a dream she felt she couldn't scream, but a nagging voice told her also 'don't give the game away. These people came to you. They went to look for you. Not to Marigold, but to you'. The world was still tilting, and it felt like she floated towards her room. It was dozens of metres to travel. Could she have blacked out? An image came to her of garbage men flinging bags into trucks, of her comically skidding all the way down the hall flung like a bowling-ball. Ah-one, ah-two, and three, throw!

It wasn't possible. She'd have remembered, she would've been even more hurt. There wasn't much pain. Lana collapsed onto her sofa next to a girl whose head lolled. There was a flicker of recognition, and the word 'fresher' flashed equally clearly in her mind.

"Lock the door." Someone protested incoherently and the first man, Schofield, said "Amy, that's not going to happen. We can't let her go. We need this." The fat man hobbled to her desk and rolled the chair. He brought her tea with him. It was still warm. The tea helped.

"Don't scream, don't shout. Not a word. It's normal to be dazed after doing that," said an American.

She nodded. The men introduced themselves, and the students too.

"On your left is April", said Schofield. "You might've seen her in lectures. She's one of your first-year students."

"Yes." She rubbed her neck. Her own voice felt distant.

"April needs your help, Dr. Peregrine. Only you can help her. We need to know everything about your accelerator."

"Please. I don't-", her voice faltered. "I can't. This doesn't make sense."

"What doesn't make sense? The fact that you've just teleported your way down the damn corridor? I think you can tell us something in return for that."

"Teleported? But how?" it's not possible. It shouldn't be possible. It violated the calm logic of normality, of standard equations and predictions and the abstract theories that lay engrained in the very marble walls of the Blackett building. Sure we talk about this stuff – everyone suggests crazy theories, or proves it given some crazy set of assumptions. There are theories, of course there are theories. But you cannot simply see it. You shouldn't be able to see teleportation with your own damned eyes. It's not possible. It would take more energy than I can even begin to understand. The tea weighed heavily on her, and as she sipped her thoughts coalesced into a sense of betrayal. Oh hell, the universe was laughing at poor Dr Peregrine and her naivety for thinking she might know a bit about how the world worked.

"Please," she said. "I want to see it. I need to see the device." She registered a drop somewhere deep in her gut when all she was handed was a small key. And on the key was a tag that read 'shift' and there was nothing else there.

"How? How does this work? Mr Schofield I need to know."

"You don't know? I understood that you would know at least something about this. I hoped you might have seen this before, or have an educated guess. You haven't seen something impossible like this?"

"No. Never, I've never seen anything like this."

"Well, you put it in a lock, turn, and that's it. That's all we know about how it works," said Schofield. "This complicates things. I was under the impression something like this key might be intentional".

"Mr Schofield, I've spent my life on Physics, I can't live with being betrayed. I need to know how it fits together."

"You're going to help us figure it out. The accelerator, Dr Peregrine. Did you use it today?"

"Yes, of course, in the morning-", she said with some surprise, and eyed Raynes "Please, I don't want any misunderstandings. I'll tell you everything but don't hurt the kids. They're just students."

"These four? They're not hostages. No, they're the ones who helped produce that key"

Lana looked through each of the hostile faces. The boys met her gaze in deep set glares. The girl who'd stopped her from calling campus security just looked to the floor. They were all filthy with streaks of mud and blood. "You made it? How?"

"We'll tell you the story when we can. Right now it's important you tell me when you used the accelerator and anything else that was scheduled for the morning," said Schofield.

"I don't know. We had to do safety checks that overran so by the time we started it was probably eight o'clock."

"Is that about right?" Schofield turned to Matt.

Matt hadn't taken his eyes off her. They'd passed museum displays in the sixth floor foyer that had been filled with gigantic parts of ancient electronic coils, copper and hundreds of pieces of wire exposed in what seemed like random connections to other wires. There was a swathe of electronic boards. Some of the parts on display were early accelerator components. They were the university's own museum pieces on its history, its achievements and the things in the cabinets had been dotted with explanations - 'complex muon solenoid', 'BaBar Experiment', 'silicon vertex detector', all of it seemed alien. When he looked at the display with its frayed wires in their '70s decay he reckoned they were just as menacing as the day they were made. And now he stared at Dr Peregrine with her tea, who'd done this to him. And he didn't know what to think. Because one half of him had enjoyed science fiction, and physics, and modern life, and knew that science had to go on and we have to progress. The university was proud of their vertex detector gleaming in its sigil geometry and rightly so. The other half loathed it, loathed her with her deer-in-the-headlights look. Eight o'clock was just about right. He and Scott had been there around then on the bridge. He told Schofield so.

"I promise," said Schofield to her "neither I nor Mr Raynes intend to hurt you, Lana, but we're running out of time to fix the problem we've found ourselves in. There was only one way to convince you quickly that you need to help us. That," he pointed to the door, "was to show you what we needed you to see."

And what was it that she saw? Did she truly see – that? The word 'teleportation' made her recoil. It was an ugly sci-fi word, a childish one, out of place and completely inappropriate for her office, or really for a technical discussion. All of it was overwhelming, too much to process: the onslaught of questions aimed at her, the nausea that still lingered. It felt like a scam but there wasn't much of a choice so Lana said "alright, how can I help."

"Let's start at the beginning. Why is there an accelerator down there?"

Chapter Thirteen – Dali Phase VI: Lana Atomica

Navari cut off a call from her bureau. The call was surreal, and maybe it was more the cold, everyday tones in which the message was delivered that made her unsure how to proceed. The person relaying the message hadn't flinched when they'd told her what amounted to insanity. She turned to Hortez and told him about the unconfirmed reports of one, possibly multiple explosions at the Huxley Mathematics Building. There was that, and the satellite and camera tracking teams that seemed to think Raynes and Schofield might be there too. She wasn't surprised that they had to resort to satellite feeds to track them and lost the kids' cell phone signals. She and Hortez had met up with Mark, and pored over his account of the day in the back of the embassy van.

"Right here?" asked Hortez. "They're still here? Why attack the university?"

"The explosions are one thing, but the bigger issue is with what the fire crews found when they went in. The British aren't telling us everything. What's certain is that the building sustained some strange structural damage. That and that there's report of a doorway made of pure blackness which imploded soon after fire crews arrived."

"A door imploded? Imploded how?" asked Hortez from the back seat of Mark's van. "Was the building rigged to blow?"

"I have no idea. There's no clear narrative – from what I understand they're two separate events. There was an explosion, and separately there's this other incident."

"I don't see how it fits together. I don't see how it benefits anyone," said Hortez. "Why blow up a Maths building when you can go for the museum?"

"We're getting helicopter support, and the British are drawing up plans for a wider evacuation. The university should be cordoned off soon. With luck we'll have a chance to ask some of the witnesses," said Navari. "Beyond that there's CTC teams on the way."

"Finally, some actual firepower," said Hortez. He caught her gaze in the rear-view mirror, and frowned. "But where did Schofield get the explosives?"

"Maybe the same place he got that guitar case."

"Us?"

"It's a possibility I've been trying to rule out," said Navari. "Mark, how fast can you get us there?"

"Ten minutes. You might be better off walking to beat the traffic," he said. "I'll try to think of anything more I can add in the meantime."

"Let's go."

***

There was a rough plan. Lana Peregrine had told them what she could, finished her tea, and they'd split their group in half: Amy, Matt, Raynes and Lana left in one while Scott guarded April and the injured Schofield in the physics office. There was a revolver and a locked door. Beyond that Schofield simply hoped that it would take time for anyone to come knocking. The building may've been close to Maths but both were enormous, labyrinthine, and maybe that would be enough.

The first group descended in the elevator to the basement, through a pair of access double-doors and into the tunnels. It was all quiet down here, and Matt listened out to catch a sound of some kind of danger - maybe footsteps, or the sound of an alarm, something, anything that would suggest you're on the right track here. There are things people don't want you to find. He didn't know what to listen for, but he expected there'd be something, or that he'd know it once he was down here. He guessed he thought there'd be cameras and that the door to the tunnels would be locked but all he got was the distant whirring of the elevator starting its way back up to ground and the sound of Lana's high-heels on the concrete. The floor, parts of the ceiling, pipes, all of it was caked solid in dust that floated when it was disturbed and glittered under the sickening mix of old sodium lamps and their blue-cold modern replacements. He had to bend to crouch under some of the hanging wires in parts, at one point he touched the walls and found they were slick with growing stalactites. There were rags to hold on to so you didn't burn yourself when stepping over the hot water ducts and their valves lay blackened and rotting in their housings. Lana wound her way through the corridors that were all identical, some with graffiti and others bare except for their laminated warnings, and she stopped whenever Raynes took out a permanent marker and drew arrows on the walls to mark the way back. Even without any evidence to support it Matt suspected it was probably stolen from the cornucopia of stationery on Lana's desk. He followed single-file behind the American and Lana in silence towards a low rumbling that got louder with each crossroad. The floor heaved and began to vibrate until the sounds of the high-heels on concrete changed to striking metal.

"Mind your head. This is the turbine room," said Lana.

It was gigantic, two-floored, the upper of which was a wide catwalk and made the room almost like a theatre for the monumental generators on stage below. There were concrete square-set pillars and heavy-duty rebar that cast deep shadows towards the far end somewhere in the darkness beyond the view here at the upper railings. Gas and water pipes criss-crossed in industrial-level chaos towards boilers through the grating under their feet and down towards the lower level. Lana gave up and took the high heels off. She crouched behind a pipe and held the shoes awkwardly when she disappeared down a ladder and into the depths.

"Go on," said Raynes. "I'll be right back after I check I know the way back and figure out how we plan to do this. Watch her."

"What if someone sees us down here?" asked Matt.

"Then it's up to Peregrine to bail you out. Make sure she doesn't try to lose you."

Matt followed Lana down the ladder and emerged between the shadowed boilers. There were two generators painted aquamarine and blackened from years of motor oil and diesel around their edges. Looking at them together side by side felt like a bizarre time-lapse. The one on the right rumbled in a way he felt through his shoes more than he could hear while the one on the left lay in heaps of disassembled. Between the two and fenced off from the rest was a transformer that was gun grey, seemed equally serious and whose humming he could hear above the sound of the generator.

"This place is filthy," he said.

"They've started maintenance on the generators. It's going to take all year to upgrade both of them," said Lana, comically small against the backdrop. "It's staggered in case the main power grid shuts off and we need the B turbine." She turned to a series of lockers on the wall nearby, opened one, took out a hardhat and high-vis jacket, then moved onto the next and did the same.

"One size fits all?" asked Amy climbing down somewhere in the aether near the boilers.

"True for everything but the boots," called Lana and threw her heels into one of the lockers, "I don't imagine anything would help us if we get caught down here but hey, at least you'll feel you're in a safe work environment."

Matt took a high-vis jacket, and Lana handed him a walkie-talkie. "Both of you have to take off any metal you have on you. Watches, rings, piercings, phones, anything at all. Do either of you have a pace-maker?" she asked.

"None of that, just this." Matt dropped his watch to the bottom near Lana's shoes. He'd looked for his phone, and remembered it wasn't there. "What about like zips and stuff? And what about this?" he held up the walkie-talkie.

"You'll be fine if it's just clothes, and we use those radios every day," she said as she laced her work-boots. "Someone once had the bright idea of taking steel-capped boots in there so as long as you don't do that we'll be okay. Where's the man, your Mister Raynes?"

"He's on his way," said Amy. She hadn't listened much when Schofield told Lana a highlighted version of what had happened to them today, and when she had tuned in it had sounded somehow alien, and wrong. There was something wrong about this, as if they were tricking this scientist, or infecting her with this parasitic strangeness that had destroyed normality. They were destroying the normal world for her too. Amy barely had a chance back in the office to think or react when Raynes took the scientist kicking and struggling to the door, and she played the scene through her mind again and again of when they dragged this lecturer, April's lecturer, back in to the office shaking to sit and listen, and answer questions about her work. And Amy had begun to think that all of what had happened today was detached from the rest of life, and that the only thing that kept her here in it was the heat and the cold that fought with one another in the same usual pattern that seemed to get faster and stronger after each cycle. There were so many things to be scared of if she opened the floodgates. The only thing they had left was to see the place where it had started, and she wondered with creeping fear what they would find, if they'd find what April wanted them to see. They hadn't spoken about that. Officially Matt was making more keys, not looking for an alternative.

Nothing. You'll find nothing down there. That intrusive thought was the worst of all because if she was wearing this hard-hat for nothing then the only thing left to do was to use the keyboard she'd unplugged from Lana's desktop and carried in a backpack she'd found, to have Matt say the keys one last time, and start this struggle all over again. For all their promises how long would Raynes and Schofield last before they turned to violence? Isn't that what Ichor had warned them about what felt like so long ago? To avoid an American and what Ichor called by its twenty-sixth century definition as a psychopath? She wondered if Matt thought the same, and for a moment could be convinced maybe he knew it too. She'd been standing here mesmerised watching the generator cycle, and saw its outline it burn into her eyes when she turned away. On top of that maybe she was dead now, maybe she just had the memories of someone else and maybe it was just those memories that saved her. But if she was dead then all those people on the other side of Schofield's black door were dead too. Maybe the return key wasn't for nothing, then. If she could help stop this place from turning into that blackness then maybe it would be worth something.

"Either way, be thankful for health and safety," said Lana. "No metal means no metal, so no-one, not us, not the army, no-one can go near the accelerator with a gun."

"The guards are armed?" asked Matt.

"Not many, but yes. They are."

"How many?" called Raynes' voice from the ladder.

"I don't know. Maybe two, three, it changes." replied Lana. "But you can't take any metal in there. The magnets will tear it through clothing, it could injure you or others."

"That won't be a problem, I've got barely any metal," he said emerging from between the boilers. "You say there's tools here I can borrow?"

"Yes. There's tools by the A generator. What do you need them for?"

"Your generators are good but rest of your infrastructure could use an upgrade," he replied.

Raynes put on a high-vis vest, hard-hat and dropped his watch next to Matt's. It still told the wrong time. Next to it he placed an almost empty box of ammunition stencilled with the words FOR HOME DEFENCE with its images of clouds, and pistol rounds. "I don't plan to take any much metal close to your accelerator, we'll be fine."

"Even at a distance it could be dangerous."

"I imagine so. Good then my weapons aren't metal."

"I see," she said. She took a few steps back behind Matt and some of the open locker doors. There was being friendly, tolerant even, given the situation but she still stayed as far away as she could, and had felt his presence behind her all throughout the walk in the tunnels. What if she took a wrong turn? The kids were alright, they were students, they were normal. How the hell had they got caught up in this? This man wasn't quite right. She watched him put on his hard-hat and cross the turbine room to look amongst parts of the disassembled generator.

"First things first", shouted Raynes from behind part of stripped housing, "I need a pipe-wrench."

"Why?" asked Lana. "Hey, why? What are you doing?"

"Aha!" There was the sound of metal clattering as Raynes tipped out all the tools he could find. "Perfect." He emerged around the other side with a few solid pieces in hand and got to work on the boiler pipes.

"Go ask him," she told Matt. "Ask him what in the hell he's doing."

"Raynes?" Matt caught him kicking a box into place to stand on so he could reach the upper pipes. "What is this?"

"What does it look like, I'm getting rid of this gas pipe. Get me a torch, Hale." he replied. "I've almost got it." Raynes turned the wrench and a thick bolt fell out of its housing. "We're on a budget here. Don't stand there, go. You think the fire department, police and secret service are going to stop their search for us? We discussed upstairs that if things went wrong we needed a distraction. This is it." Matt crossed the main empty part of the theatre-turbine room and found the bag of tools. Schofield and Raynes had looked at one another meaningfully in the office when they'd spoken about a distraction. He didn't like the sound of this.

"Well?" asked Amy.

"Well what?" asked Matt. "He says he's setting up a distraction like we planned."

"So what are you doing here?"

"Getting him a torch," he replied. He heard another bolt fall free of the rusted pipe and together they found a handheld one that was powerful enough to cut through the darkness beneath the boilers. They held it for Raynes as he finished off the last of the bolts. The plastic box Raynes had stood on was kicked a few feet across the room so that he could reach other end of the pipe.

"Put some boxes down or something on the concrete to dampen the sound when this pipe falls," he said.

"But this whole room will fill up with gas," said Amy.

"That's the general idea," came the reply. "Watch these bolts don't hit you."

It went easier, and Raynes undid all but the last bolt, which sheared itself as the whole pipe segment fell to the ground to crush the cardboard. It wasn't perfect and it rolled to slam against a boiler.

"That'll do it," said Raynes. "The flow in these pipes is pretty slow but they're wide-bore. Still, you could stuff a rag in there and it would stop the flow. Let's hope no-one does that."

"You want to blow up the turbine room?" asked Amy, "That's the distraction to buy us some more time? What about everyone upstairs? Above us there's lecture theatres, buildings, Lana said there's the entire engineering building on top of us this side of campus. Dr Peregrine, tell him."

Raynes got down from his box before Lana could protest. "We don't want to blow up this turbine room, but we sure as hell are going to blow it up if we need to. Besides, it'll be almost five o'clock, and we're deep underground. The chances there'll be anyone down here or many up there are low. Now, get some rags. You'll need to come back through here later to get back to Schofield. We can't have you falling unconscious in here."

Amy didn't know how to respond. The idea of doing this, actually setting a gas explosion was almost too far, would be too far in any other situation. Maybe it would be satisfying to watch this place go, and maybe it wouldn't matter in a few hours if everything was going to disintegrate like the black door. "This room supplements power for whatever lies behind your steel door, right?" asked Amy. She turned to the scientist who now stared back at her in horror.

"What if we need the Atomic Vice to undo this?" asked Matt. "April's gotten us this far. She says it's important. We need to trust her. You can't just blow it up, Raynes."

"Like I said - we won't if we don't have to."

Raynes dropped his pipe wrench and watched it thwack onto the cardboard to lie next to the wide-bore gas pipe. "Schofield's injured upstairs thanks to your friend here, Matt," he said. "Sooner or later he'll need a hospital. We need to either understand this thing right now, today, or buy ourselves enough time to get him to one. Got it?"

"We need to trust April," said Matt. "She's got an entire month's worth of knowledge."

"And she's delirious. We need to go. We've got this part finished. I'm just going to go set up the transformer. Lana, you know what you need to do when you get down there?"

"Yes. I do," she said.

"Here's one of the keys then." He showed it to her. "Do what you need to. Distract him, keep to your story but most of all remember that this is a key in the 'instant' category, just like back in your office. Same deal, it's just as insane. If you're the one to turn it in a lock, you'll be the one who goes, instantly. The door doesn't wait to be opened."

"Okay," said Lana, and took the 'home' key from Raynes. Checking the control key list didn't lie. 'Name – home, Function – sends user to a location considered home, Type – transfer instant, Location - variable'. The 'home' would do just what it said.

Raynes took his wrench and rummaged around behind the broken generator for supplies. He smashed the lock to the cage housing the transformer, made the gate seem closed and spent some time working with the wrench underneath the machine. Soon enough he finished his trap, latched the cage surrounding the transformer closed, and put his tools away hidden in the housing of the disassembled machine.

"Okay. We're done here. Lead on, Doctor. We're following you." So Lana did as she was told and they went single-file through a backstage side-entrance of the turbine room theatre and emerged in the restricted half of the tunnels that ended in a steel door at Hyde Park. After a few steps she came to the first T-junction that joined onto the main artery linking the university to Hyde park past a sign saying 'Authorized access only.' The ceiling was higher than they could reach if they jumped, and there were fewer pipes, with those that were there hanging in huge steel cages. The entire tunnel was domed, in fact, and its curved walls shone in glazed ceramic bricks. Raynes stopped her.

"Why do I hear voices? You said the facility was far."

"If you turn right at this junction and go down there," she pointed "you'll come out through a door and into the underground walkway that goes between the Science museum and the other museums. It goes all the way to the tube station. This part's been blocked off and the other part's public but it's the same tunnel."

Raynes pointed the flashlight down the unlit part of the main tunnel on the right. It ended abruptly in the same white tiles. On the left side everything was quiet. "Where next?" he asked.

"We go left and northwards." Lana went first without her torch to swing side-to-side. Up until recently she hadn't quite remembered where Hyde Park was. Then Schofield and Raynes had taught her to count.

"It doesn't look like it's been cleaned in forever," said Amy. "I keep kicking bricks". The echo carried, and in the half-darkness she realized that down here it felt a little like Otter's world where there was nothing but footsteps and echoes and old ruins.

"I don't know if the tunnels are post-war or not. God knows. It's always been like this." said Lana. "Others in the lab say it's been like this at least since the '70s."

"How far do these tunnels go?"

"They end at the other side in the military barracks, and they keep that side of the door clean enough."

"Why put it all here, though?" asked Amy. "This is the middle of the city."

She couldn't read Lana's expression in the limelight. "As far as I know it was tunnels first and then they shoe-horned in the accelerator later amongst the rest. Security for Exhibition road's important. It always has been an important place because there's three museums-worth of artefacts to save in a crisis."

Amy tried to imagine how large the vaults would have to be for that, and couldn't begin to compute it. She imagined wheeling all the art and bones and scientific history on the carts through this corridor, the curators flanked by army, maybe herding students to shelters here to wait out whatever catastrophe. She'd walked the public underground passage on the other side of the wall from the museums to the station dozens of times. Every time she needed to catch the train home or go for a night out, or visit a friend she had to walk from her room with its stacked bowls in their halls of residence, pass April's room to go up the staircase, out the door to South Kensington Tube and back. When it was cold the underground walkway was always the best route. This was its mirror image, derelict, familiar, distorted. Where there should've been schoolkids and buskers there was nothing. There should've been exit-tunnels and stairs from the underground to the world above. It was just one long corridor, wide as a tube station with the lamps stretching off sparse and even into the darkness.

"We're almost there. We need to take a right here at this third tunnel and head down the stairs," said Lana.

The side-passage was so dark Amy would have missed it completely in the gloom. There had been alcoves everywhere, debris, pillars. Raynes scanned the walls with his torch. It barely made a dent on the darkness. He found a sign.

"DSTL site," he read. "Access restricted. How much further from here on out?"

"Through here and down the stairs takes us most of the way. It opens up into a corridor that winds its way north again. That's it. There aren't any more junctions."

"And the cameras are only at the door?" he asked.

"I think so. I don't remember."

"You think so? You're not certain."

"I hope so," she said.

"Lana, take a deep breath. You've found this key, and you just want to check if it fits in the door. That's all. That's the story. You found this copy on your superior's desk, and you feel they should've returned it. It'll take thirty seconds, then it's over and you just call us on your radio. We'll be a bit behind you."

"That's all. Half a minute."

"That's right."

She entered the corridor feeling for the corners of the brickwork to guide her. The gloom sharpened and she began to see the outlines of other bricked-off passages and obstacles. It got lighter until she turned to find the final stretch of the corridor and the familiar steel door in the middle distance. It was alone and lit with a single industrial cage lamp. She should've brought the torch with her. No-one would normally come down without one. One moment she was approaching the door and what felt like horribly too soon she was suddenly knocking on it. After a moment it opened. She unclipped her badge and recognised the face behind the door as the same one who was on duty in the morning. She panicked, tried to remember his name.

"Hi James," she said, and passed over her pass. "I forgot some data. How's it going?" Keep your voice neutral. Resist the urge to shiver, or do anything. Relax. Just stand there and talk, there's nothing wrong. It's just a normal day.

He scanned it and opened the door fully to let her in. "It's slow as ever. You got anything for the X-ray?"

"Nope. Even forgot my torch in the rush." The lone X-ray belt and its metal detector were barren. For the major morning shifts and evening ones they army would bring in someone to run it and avoid delays. At this time of day it lay deserted.

He bolted the door shut behind her. "I swear I can feel myself getting paler every day. I don't know how you survive."

"A lot of coffee and vitamin D supplements is the only way," replied Lana. He patted her down, and she went to walk through the metal detector.

"Oh, I've found this key today. It might set off the detector. Is it alright?" She handed it over. "It was on Marigold's desk, and I just felt like there was something off about him. He wouldn't tell me what it was but I overheard him talking with someone from maintenance about access down here." James inspected the key. If only he knew how cold her hands were when she'd given it to him, how close they were to shaking.

"Professor Marigold? The one in your department? He worked the night yesterday I think."

"Yeah, late-fifties, about this tall, slightly on the weighty side. Do you remember, he brings in like the same sandwich and banana every other day?"

"Oh, him. He was talking about access using this?" James' face creased. He might be a guard, and one she knew well, but he was still a soldier with a beret and full khaki uniform.

"The idea seemed to be that he hates having to bring someone down from the main office and asking them to be let out when he works late. I think he borrowed this key and, for whatever reason, it was never returned. That's the gist I got from it. I don't know if it's true, but I thought it's best to just check with you guys."

"He does maintenance on the accelerator?"

"From time to time. I think he works with the engineering team to improve things."

James put the key aside and went to the phone. "I'll call to see if they've given it to him."

"No, wait," said Lana. "It's just a suspicion. I don't even know if it's a key to this door or not."

He put the phone down, shrugged and compared the key she'd brought to his own set on the table by the X-ray machine.

"They look similar," he said. Please God let this work, she thought. The soldier turned his back, and she heard him for a moment put something in the lock, and heard it clunk.

"Seems like-"

He vanished. Lana fought against taking a step back. So it was true. She wasn't insane. The world had gone insane. It didn't sound likely, but here she was. Mid-sentence. He'd been cut off mid-sentence and was just...gone. She stood perfectly still like that for a while, long enough for the cameras to wonder if maybe it was just a glitch. She hoped no-one had been paying attention. It was the wrong time of day to be watching the camera feeds closely and there were other priorities for the military around here. Maybe, just maybe, she hoped, if anyone was watching they won't believe what they saw. Either that, or they'd chalk it up to a camera error. How long had she been frozen like this? It couldn't have been more than a few moments, seconds. There wasn't the sound of any alarm so she picked up the keys, disarmed the 'home' as quickly as she dared and unbolted the door.

"Raynes," she hissed, "Amy. Matt." Maybe it was too far to call for them. If they couldn't hear her she'd have to use the radio but security definitely listened to the radio frequencies allocated to them. You couldn't keep the door unbolted for long either, she suspected. There's a reason why the guards only let in a few people before they had to close and re-open it up again even when it seemed inconvenient and pointless. Lana tuned her radio, tried channel two that they'd agreed on and got no response. Short messages might go unnoticed and she gambled with channel eleven, one that they almost never used.

"Do you read me?" she asked. There was no response. If Matt didn't have the radio on then there'd really be no easy way to do this. She held it, waited, listened through the static. There was a rap on the door, and she opened the door.

"Great work," said Raynes. "Did you have any trouble with him?"

"No, it worked. I didn't hear any signs of trouble, but they could have silent alarms."

"They do. I've already been asked by radio whether everything's alright down here," said Raynes. "I figured that meant you must've gone through with it."

"You didn't hear my message?" she asked.

"No," he replied, "but hopefully my reply bought us some time with security. We'll see." He shut the door behind them. They passed through the metal detector without it detecting much, and headed down a worn corridor clad with linoleum. This part of the tunnels was maintained, clean but worn with swinging school-like doors and long gashes in the walls from countless carts and scrapes. Overpowering it all was the mixed stench of acrid metal, cleaning fluid, and something burning.

Lana walked with purpose through the corridors and saw no-one up close. She didn't stop, and didn't falter. Distant figures used forklifts to arrange supplies, other times they spotted researchers carrying empty mugs in jumpers, collared shirts and jeans. She powered ahead through it with her key-card, directed them through the unmarked passages to lead them towards the Atomic Vice. There was no time to waste here. An ancient swing-door let them into the control room. It was real, thought Amy. And with that thought came the anger at it, the fury that all of this been here, so close to the public. That and the fact that if not for April they'd have no chance of finding it. They descended the steps to the accelerator control room.

There were concrete walls, bolted banks of TVs on top with close-circuit feeds of the length of the synchrotron in monochrome. There was the control stations for the low-level linear accelerator that ran pre-millennial software, others for the booster loop and finally a whole bank of much newer PCs dedicated to data collection and monitoring magnetic fields and operations of the newest and largest part of the Atomic Vice. Lana scanned the room, looked to the radiation warning light, then across the bank of CCTV. Good. There were no experiments running and this afternoon was a maintenance day. Those inspecting the magnets and the liquid helium cooling on camera A5 would be a couple hundred metres out on the other side of the loop. She checked the office partitions.

"Hello? Anyone? Angela? Frankie? You guys here?" she asked. There was silence. Maybe Marigold had found something wrong with the liquid helium after all. "Do you see anyone from up there?" she asked Raynes who stood by the door they came through.

"Nope. All clear from this angle."

"Then help me barricade this," she replied. Lana struggled with a filing cabinet beside the door marked with the radiation warning light. They helped heave it into place, but not before Amy had a chance to look through the leaded glass to get a glimpse of the machine itself. It was gigantic, a confused corridor crammed on one side with giant bore pipes and clad in a forest of wired debris on all sides. There was the distant high-pitched whine of something unnatural, and the door itself felt even more serious and cold than the others. The thickness of the glass betrayed the true weight of the containment needed.

"I've found a laptop here that's logged in," said Matt at one of the stations.

"I don't know who's that is, maybe Marigold's. It's not Angela's, and that's her desk."

"This tea's still warm," he said.

"Which is why we need to hurry," replied Lana. She rushed to her console and logged in. "If something strange happened this morning, I need to find it in this data."

"How old's this computer?" asked Amy.

"Old for the two-thousands, beyond high-tech for 1995. Is this really the thing you should be focusing on?" Vector graphics and old-style welcomes blazed into view almost instantly. Some of the earliest things here ran on floppy disks and duct tape. It wasn't for a lack of money, or effort. It was just that if you started messing with calibration and programs running the oldest booster loops and the starting accelerator there'd be down-time of maybe a month, probably more. Some experiments take days, others need months for consistency. The floppy disks were kept closely-guarded. She opened up the runtime program and data from this morning.

"Do you see anything in the analysis? Anything weird?" asked Amy.

"What's that?" Matt pointed to Lana's screen.

"Let me work. This is just the power readout. If there's something strange, I'll find it. Focus on helping Raynes keep us alive."

They left Peregrine calculating at her station. There were dozens of computers here, all on standby. Saying 'the keys' here wouldn't be good, but it was close to the time when they might have to. It was either saying that, or saying something else. Somewhere here there'd be the report April wanted her to find. It had seemed vital. I'll try my best, Apes, we'll try our best to end this all.

"Matt, search this side for the thing we spoke about, the April thing. I'll do the cabinets over there."

"Did she say anything more?"

"Just what I told you. Use your instincts, Matt," she said as she sifted through papers. There were purchase orders. Readouts. Graphs. Emails. "Go on. Start looking, it's almost time one way or another. Either you're saying the keys, or something better", she whispered. "We think of a better idea than blowing up the tunnels as a distraction."

"I thought we had some time before I needed to chant something."

"That's just what I told Raynes at the office."

Amy ripped out the shelves of the cabinets and threw out folders. Efficiency reports, readouts, budgeting, printed articles from Science magazine. Matt disappeared and searched through papers, drawers and stationery. A to H and different project names. Nope. She tore the drawer off its rails and dropped it. She went through the desks, turned on their lamps and tried computers.

"Any luck, Lana?" she asked.

"Nothing...qui-i-ite yet. Everything looks normal."

A filing drawer clattered to the floor. Raynes shot her a look from the main entrance. "Keep it quiet."

She kept going. If Raynes thought she was searching for proof of some kind of illicit experiments then all the better. Only Matt and she knew what April had said about finding something called an S552 maintenance report. If April thought it was their best bet, Amy believed it.

She stormed to the next desk. There were post-it notes scrawled and left on the pre-millenial yellow custard monitor. 'Marigold, see Jack for the updates this afternoon. Thanks.' Amy looked around the corner of the desk partitions and saw Lana busy at the other end. She wasn't sure if she cared whether Lana approved of going through all this stuff. This desk drawer was locked. The files left on top of a closed laptop were not. She opened them. There was a stapled copy of the updated safety protocol and she supposed that was this person's signature, this Professor Marigold, on the risk assessment forms that listed different hazards in their cheerful tick-boxes. And next to it were a few sheets for the updates as to the state of the machinery. She read the title. S552 Accelerator 'Atomic Vice' Power Maintenance Report, May 11th.

It was a report like a lot of others and almost missed it. She felt light-headed and shook as she leafed through it. Tables of contents, charts, action points marked at chapter 3.2 for improving safety and cooling. Only crap. She read the title again. A power maintenance report. POWER maintenance. It doesn't specify what kind of power, electric, or Matt's...or. She took it again. This thing could be turned into a report on how to maintain Matt's power?

"Lana. Hey, Lana," she grabbed her shoulder.

"What? I have maybe another ten minutes to analyse this all. Just-"

"How often do they make these?" she held the report in both hands. "This one's from today."

"The safety reports? Every quarter, or every month I think. But do you thin-"

Every month. They make these every month, so that means that they made the last one in April. And if they made the last one in April then she knew about it, and if it's a power maintenance report for the accelerator then...well, maybe April was right. Matt didn't have long. She caught him ripping apart files from parts of the filing cabinet barricade for clues.

"They've been doing this for years," he shouted. "Look at this, look. This one dates from '94."

"I've got something." She handed him the report.

He stopped. "What?" He scanned the pages. "A power report? Like, power and other kind of power?"

"Hey, wrap it up!" shouted Raynes from out of sight.

"I'm not done yet, it takes time," said Lana.

"You see that wall of CCTV cameras?" said Raynes. "They're coming back."

Matt stuffed the report into his jacket as Raynes rounded the corner. "Help me out here," he said and looked from one to the other. "Brace this cabinet with me."

They put a shoulder to the barricaded cabinet bank and Raynes kicked some of the spent folders out of the way. The handgun came out by his side. Four magazine will have to do, he reckoned. "It's still better than the time in Dubai", he whispered to himself. That could change. The cabinet shuddered as someone tried to open the door.

"What the hell?" came a voice from the other side.

Raynes signed at them to keep quiet. Lana stood up from her work and looked over the office separation. Don't panic. There was time, and she could run more tests. She felt as if she was looking at herself from very far away, sat down and typed out the next analysis command. Why did I agree to this? Prison is the only way out now. No, maybe I can say I was a hostage...but, she couldn't think of the details now. Focus on the task at hand. This would take too long, and she knew it. In the depths of her stomach she thought she already knew what the result might be. There's nothing strange here. There's nothing in the readouts, the tests are to double-check something completely null in the United States. It was a normal run, and comparing it to the previous run they're the same.

"Agh". Raynes grunted against the blow of someone slamming against the cabinet. The cabinet let out a dull gong and held in place. His radio blared through the static of the deep rock and clay in garbled voices. Snippets of conversation could be heard. Control room west. I repeat control room west, what's your status? Is there an emergency-".

"Amy, how long to more keys?" he asked.

"Soon," she said truthfully. But it wouldn't be the keys they'd be saying this time. No, if Otter had taught her anything it was that she couldn't look back like that, get focused on one approach.

"We're leaving. Forget the door," said Raynes. He went to Lana's desk "it'll take them a few minutes but we have to go." He leaned over her desk.

"How are we doing? How long?" he asked.

"It won't be done," she replied. "This can take time, there's gigabytes of data. And I see nothing weird, there's nothing obviously strange that could explain this, whatever this is."

Raynes was out of mints, and this was a critical time. "Take us back." He slammed open the main door and cleared the entrance for Lana to get them out of here.

***

Bianca,

You asked me once how I finish my famous carrot cake and I'm starting to realize this may be my last chance to come clean. The icing is full fat cream cheese, generous amounts of vanilla extract and a pinch of sugar. Leave it to chill in the fridge for at least half an hour or longer to be certain it's solid enough to decorate. Any less than that and the whole thing could collapse. Trust what you saw last time we met, we may be the only ones still sane.

P

Navari folded the letter through a tissue and thrust it back to one of the police officers. It had been written on the back of an Official Secrets declaration. For a moment she betrayed a pang of nostalgia for the time Schofield came all the way to the Embassy to thank them with his home-made recipes. "Did you just say no to a second slice of my carrot cake? Impossible. I've already cut it." But to do this to mock her? The letter was dropped into an evidence bag, sealed. She'd got here late with the gridlock, and by now the Huxley Maths building was flooded with heavy-set Kevlar and tactical belts. Detectives were the most recent addition and had begun photographing the ruins of the computer room. Scattered forces from the CTC counter-terrorist command task force were stretched increasingly thin, but a deployment of them had just recently arrived. She saw the tension in the movements of the older folk from the IRA days who still had the itch in the back of their mind wondering if there might be a second bomb. The first hadn't killed anyone, hadn't been called in or claimed yet. Everything about the police analysis was methodical, fast. Get in and get out of the building as quickly as possible. The bomb sniffer dogs could fail, or there could be radiation. You never could be sure.

"Excuse me, just another thing before you go," she asked the officer who'd shown her the letter.

"Yes ma'am."

"Which way to Hyde Park?"

"Sorry?" the officer frowned.

"Which way is it from here to Hyde Park? Where is it?"

"Mmm..." he said with notebook in hand and started to sketch something "bear with me on this". He stopped with the roads half-drawn, laughed. "It's not coming to me, I don't know." He circled something. "I think North somewhere. Sorry about that."

"Oh no, you don't have to, it's fine."

The officer made his way down the maths corridor and crunched fallen glass. "One moment, let me get someone who might know."

"Really, that won't be necessary."

"Jim. Hey, Jim, come here," shouted the officer across the throng of uniforms.

"We've got it," she called back. "Thank you." The officer gave her a thumbs up and returned to his station by the stairwell. We are the only sane ones.

She saw the glances she got from the team up here, the cool reception from all but the police at the lowest rung who didn't know who she was. They all thought she knew something they didn't, and they'd all read the letter addressed to her. Some of the people here had met Schofield, and she thought they probably hoped against hope he wasn't the traitor. And to them if it wasn't Schofield then maybe it was the Americans who'd done this. In their minds this could be Raynes' or her doing to try and gain some sort of advantage, or move closer to one of the unseen and unknowable goals of dark rooms in Virginia.

Chill for half an hour or longer, said the letter. She looked to her watch and noted the time. Fine, you have half an hour's head start. Again, Navari, you're giving them the benefit of the doubt. On one hand she thought she knew Schofield. He had to be a traitor, a spy for the other side (whatever other side that was). It had happened before with the likes of spies like Kim Philby, and it could happen again. But Kim Philby never made a whole park disappear when he defected to Russia, and never took a step back to vanish into thin air. We are the only ones left still sane. She didn't feel sane, but maybe she was. Those keyboards, if anything, she thought when she looked to the destroyed piles of plastic and metal, aren't sane. No explosives or known propellants were identified from the quick field tests. There was nothing to suggest that the keyboards had been tampered with, only testimonies from students that they'd been asked to leave the room by two men they assumed were lecturers. So if Schofield knew about the bomb then did he try to prevent casualties? Or did he plant it himself?

She turned to Hortez. He was inspecting the obliterated doorframe to the maths lab. It was complete savagery, as if an animal had hacked away at the plaster and metal to the very core until the entire frame was smashed to pieces. There was metal joists that had been sheared clear off the ceiling and they'd had to bring in engineers to prop up the ceiling around it with jerry-rigged scaffolding. It was that bad. One of the doors was missing, gone completely. An entire lab-grade positive airflow door that was supposed to keep the servers and the heavy-hitting computers at peak condition was completely missing. There was not a screw, wood chip, nothing. The lab floor seemed clear and just shone with puddles from the flood. Thankfully the most expensive of the lab electronics seemed dry.

"I've been thinking," said Hortez when approached.

"For once?"

"Sure."

"Me too," she said. Her shoes were soaked. "Any of this look like it adds up to you?"

"Not this," he pointed to the destroyed doorway. "Not even close. This," he said "is complete batshit."

"Well said."

"But the keyboards over there, those I think I know. It's the same as the park."

"I think so too. The barricade of tables was there for a reason. This is it," she said.

"This is it. They wanted to do this, somehow, to a computer," said Hortez. "But the motivation isn't to cause damage."

"No, if they wanted to destroy something they'd not try detonating it in the middle of an empty park," reasoned Navari.

"Testing, then?"

"But what's the method? How do they detonate?" she asked him. "And what" she whispered "the fuck is up with these keys? Explain that. What in the fuck is that, Hortez? Who does that? Who drops hundreds of keys?"

"The lithium-ion laptop battery I could understand exploding," replied Hortez looking through the lab. "Run some malicious software, overheat it, whatever. Maybe if you modify a laptop it could explode." The door was still missing, no matter how long you stared at it that didn't change. "But these keyboards have nothing that could do this. They have no power in them, they're on USB. There's no battery. There's nothing."

"So the keys then?"

"Have you seen them?" asked Hortez. He looked at her with an expression of puzzlement that seemed foreign on him. It felt as if all of what was around them had finally hit home. "They're labelled. Goddamn labelled with letters and shit."

"Silence of the lambs has moths. Some murderers have origami. Schofield has keys."

He dismissed her. "That's not it. You know my opinion of Schofield. He's sleazy, he's weird, he's just off for me. Great guy, maybe," conceded Hortez. "Not for me, but maybe a great guy for some people." He kicked some glass from under his foot which skidded and somersaulted through the puddles to meld into them invisible once more. "But Mr Washington is one of us. I know Paul. Paul, no." He shook his head. "Paul wouldn't pull this."

"No he wouldn't," said Navari. She read the files of most of the agents that came through London under her jurisdiction. There was the terrible truth that during the firefight with Raynes she'd leaned out of cover quite a few times thinking she had the element of surprise. It was only later she began to wonder if Paul Raynes didn't miss at two-hundred metres with that many rounds only if he wanted to. She had her doubts buried at the back of her mind about Hortez too. She'd reasoned with herself that on one hand the Barratt was a different rifle to what someone like Hortez was used to, and it was intended for vehicles more than people, for God's sake. The velocity, the drop, the recoil, it would all be different. Even so it was strange for him to miss the last few shots. But this was a strange day. She made a decision.

"Have there been any updated sightings?" she asked.

"Unconfirmed only. At least five."

"By satellite?"

"By CCTV only across South Kensington," he replied. "And nothing useful on campus."

She frowned. "Did they get back to you about the satellite request?"

"Too many simultaneous operations at short notice. They couldn't spare one."

"What? Was that the excuse? That's moronic. This is a crisis. Hortez, we don't know what this thing is. No-one knows where Hyde Park is on a map unless they use a dumb nursery game."

He shrugged. "You know it gets political. London, Western Europe, you know how bad that looks if we do a flyover."

"But CCTV tapping is fine? That's just...wow." She looked out of one of the windows of the maths lab. The scene had changed. More reinforcements had arrived, and likely not just on this side of the campus. The worst thing to do was to start a public panic. A thought struck her.

"Why didn't they just tell us there was a bomb threat here when they had the chance?"

"Maybe they found out recently. Maybe they didn't know where it would be", replied Hortez. On the street men spilled out of the armoured vans to take up positions. The same vans were stretched thin – between the reports of heavy-calibre gunfire coming from somewhere no-one seemed to be able to find and the city's largest illicit arms bust the city's counter-terrorist squadrons had struggled to arrive on time in great enough numbers.

"Why fake their own deaths and still try to stop it, though? And the students with them are what, hostages?"

Hortez didn't have an answer for her. "There's a few who think they might be linked to a strange spike in data that was downloaded this morning. They don't know how far it goes, but they said it went pretty far. It might be Chinese but probably not. It was a program that seemed to be limited to downloading public domains, which, yeah, I don't get. We think it's part of what Raynes and Schofield were following up."

"How does that fit in?" She dismissed it. Things were complicated enough without more elements and theories clouding her mind. "Everything has been centred on this area. Why?"

"Maybe there's something around here that they want, or can't defect without. Hell, this is the computing department, maybe it's related to the hack?" said Hortez.

"So they're probably still here," she said. And looking out of the window she knew that if that were true then it was a matter of time before they'd be found. Trust what you saw last time we met. That was the real problem. That was the one unexplained part. Alright, Bee, time to convince a chief officer for counter-terrorist command not to escalate this, to wait a little while longer before evacuating all these buildings. Time to buy Schofield half an hour. But when she looked out towards the vans she saw the decision had been made already and made in force.