I poked my fork into the Z stamped into the waffle’s centre. ‘It looks like the mark of Zorro,’ I joked.

‘Yeah.’

Maybe they don’t have Zorro in Norway. She looked at the sleeping bag on the floor. I suppose she noticed the rifle, too.

‘Working hard?’

I had to tell someone or I’d go mad. ‘This is going to sound crazy, but I opened Martin’s email last night. I found a message from a colleague in England, someone who’d reviewed his results from the big Nature paper last year. He claimed Martin doped his samples.’ I explained about Pfu-87 polymerase. ‘It’s an enzyme to make the DNA in the water combine and evolve much faster than it would naturally.’

Greta shook her head. ‘Martin wouldn’t.’

‘I don’t think he did. He was as surprised as anyone. He knew there’d been trouble replicating his results. That’s why he came back here to overwinter.’

I unrolled the map where I’d marked his samples. ‘You can see what he was doing. All through the winter, collecting samples around Zodiac, trying and failing to replicate his own results. He didn’t understand why it wouldn’t work. That’s why he was so down.’

I moved my finger up to Echo Bay. ‘Then, in March, Quam sent him to help DAR-X with their leaky gas pipes. That was the breakthrough. Martin analysed the water there, and found it was bursting with these little organisms feeding on DAR-X’s pipes. I’m guessing that made him wonder how they could have evolved so quickly, and reproduced in such numbers. So he reran his original experiment using water from Echo Bay. Bingo.’

‘Are you sure?’

‘Martin’s original sample, for the Nature paper, came from a summer trip to Gemini.’ A shadow crossed Greta’s face. She must have been thinking how Hagger had kept warm at Gemini. ‘He went down to the Helbreensfjord and got a sample. Pure chance. When he came back this winter, he stayed close to base.’ She still looked sceptical. I pointed to the machine on the bench. ‘I’ve analysed all his samples. All the ones from between the Helbreensfjord and Echo Bay — the red dots on the map — contain high doses of this enzyme.’

‘OK,’ she said.

‘But that’s not the crazy bit.’

‘OK.’

‘My PhD was on polymerase enzymes — specifically, on Pfu-87.’

‘With Martin?’

‘A guy called Richie Pharaoh. I switched PhD supervisors after my first year.’ That was a story I didn’t want to go into. ‘The point is, Pfu is a naturally occurring enzyme. It was discovered in bacteria that live in volcanic vents on the ocean floor. But Pfu-87 is a synthetic variant, a version that’s been genetically tweaked in a lab to work better. It doesn’t occur in nature.’

I realised I’d begun to tremble.

‘And that’s the crazy bit? Because it’s man-made?’

‘The crazy bit’ — the reason I was holed up in the caboose with a gun — ‘is that I invented it. I made the modifications. That was my PhD, and the paper I published. Martin had a copy in his lab.’ And I’d thought he was just checking my credentials. ‘At least now I know why he brought me here.’

Greta thought about that. ‘So one question.’

‘Only one?’

‘Why is the Helbreen pumping out this DNA chemical you invented?’

I wished I had a good answer.

‘I have to go fix the satellite dish,’ she announced. ‘If we don’t get the Internet back, people will start eating each other.’

Her question echoed in my mind a long time after she’d gone. Why is the Helbreen pumping out this DNA chemical you invented?

Answer: It isn’t. I’ve tested all the samples Hagger took from the glacier three times over. No Pfu-87, from the top of the glacier down to the very front edge. Nothing until you get into the seawater below the ice. All green. As if it’s just welling out of the seabed.

I was still thinking about it an hour later when Eastman came through the door. No knock, and I’d forgotten to jam it shut after Greta left. My rifle was on the other side of the room.

He smiled that brilliant smile, though it didn’t have quite the same wattage. As if the bulb was going. His face was red, his eyes were bright and he spoke too quickly.

‘What’s going on?’

He was jumpy. Literally: he couldn’t stay still. If I’d been stood near him on the platform at Cambridge station, I’d have assumed he was a drug addict.

As blandly as possible, I told him I was working on Hagger’s old data.

‘I heard they were bullshit.’ Succinct as ever. I wished Kennedy hadn’t shown him the email.

I explained why I thought Hagger was innocent, leaving out the Pfu-87. Eastman didn’t seem to pay attention. His eyes were always moving, taking things in at a thousand frames a second.

‘What are those?’ he said, pointing to the machines.

I couldn’t tell if this was just a prelude to an act of violence. I mean, I’ve seen enough films where the psychopath makes conversation about cheeseburgers or parking wardens and then suddenly smashes his victim’s face in. I played along, and tried to edge around towards the rifle.

‘Do they work?’ he said.

‘Perfectly.’ I could almost reach the rifle, now. Eastman must have noticed. His arm suddenly shot out to block my way, thrusting a sheet of paper into my hands.

‘I got another reading on that interference.’ The paper was covered with noughts, ones and twos, the same as the one from Hagger’s notebook. ‘Looks like it’s coming from near Vitangelsk. Up by Mine Eight.’

He leaned very close to me as he said it, as if I was a pretty girl at a party. Like the girl, I couldn’t do anything except shrink against the wall, and wish I had my gun.

‘If only we could unlock it.’ Heavy emphasis; in case I missed it, he mimed turning a key with his hand. ‘You know, with a key.’

It wasn’t subtle. So I’d been right, the key must have been his — dropped where Hagger died. I tried not to show that I’d guessed. He’d kill me right there.

The sequencer beeped and broke the moment. The printer chattered, and a spool of paper came out. I tore it off and jammed it in my pocket before Eastman could get a look.

‘Have you ever been to New York?’ I asked, thinking of the bear on the key ring.

Thankfully, at that moment Kennedy came in and announced that Quam had gone to check one of the bear cameras. It must have meant something to Eastman. He left so quickly he forgot to take his paper.

As soon as he was out the door, I barricaded it with as many boxes as I could find. Which meant that when Greta arrived, five minutes later, I had to move them all over again. No waffles this time; she didn’t even ask about the elaborate barricade. Her face was red, almost as if she’d been crying.

She fell against me. I just caught her, holding her to my chest like a hurt child. Her body convulsed with silent, tearless sobs. I didn’t know what to do, except pat her on the back. Then, without thinking, I started to stroke her hair.

She pulled back from me as if I’d burned her.

‘Don’t—’

I held up my hands. ‘I’m not … I wasn’t …’ Took a step back. Asked, ludicrously, ‘Are you OK?’

She stalked across the room, head held so stiff you could have cracked bricks on it. Glanced at the readouts on the machines. She still looked as if she might burst into tears — or bite someone.

‘It’s nothing.’

‘Really?’

‘I had a bad experience.’

It’s the sort of statement that ties me in knots. I want to help, but I’m petrified of being thought intrusive. A very English problem. I’ve always envied the people who can just throw their arms around complete strangers without analysing it from twenty different angles.

‘Do you want to talk about it?’ I tried.

‘No.’ She flexed her fingers, as if imagining closing them around someone’s throat. ‘You know why I came here? To Utgard?’ I shook my head. ‘To get away from all the assholes.’

Something on the workbench caught her eye. She picked up one of the plastic bottles lying there, spun it in her fingers, then threw it against the wall like a fielder shying at the stumps. ‘Asshole.’