Of course, we didn’t have a body bag. We zipped Hagger into a sleeping bag from the emergency box and pulled the hood tight around his face. A tuft of his beard, frosted with ice crystals, stuck out.

The sun had come up. I felt the weariness of having seen a long night through — though really, it was only three in the morning. Greta fetched the sledges we’d left up the hill, and we strapped Hagger on the one I’d brought. In case we have to bring anything back.

‘You take the emergency sled,’ Greta said. I was grateful. I didn’t fancy three hours dragging a dead man.

I pulled the starter cord and gunned the throttle. The engine roared, but the snowmobile didn’t move. Maybe the weight of the sled? I added more power; I smelled smoke. Too late, I saw Greta waving angrily at me.

‘You forgot to loosen the tracks,’ she shouted.

I jumped off as if I’d been shot. Together, we heaved the frozen tracks off the ice. I smelled scorched metal.

‘Will it be OK?’

She shrugged. ‘It’s a long way home.’

We followed our tracks back up the glacier. I tried to look at the ground, and not at the stiff bundle on the sledge in front. There were an awful lot of implications wrapped up in that sleeping bag, but I didn’t want to think about them.

And then I couldn’t. The engine note changed; I felt the power sapping. Every time I eased a fraction off the throttle, the engine stuttered as if it was about to cut out. Twice, I rescued it by jamming on the throttle again. The third time, it died.

For a heart-stopping moment, I watched Greta carry on into the distance. Then she circled round, drove back and pulled up beside me. She flipped up the snowmobile’s plastic nose and peered at the engine.

‘Kaput.’

The day had actually got darker since sunrise. Clouds had blown up, fed by a wind that scoured the ice dome. The moment I opened my visor, a volley of ice granules peppered my face. I didn’t know exactly where we were, but I knew it was still a long way from base.

‘Can you fix it?’

Ignoring me, she reached inside her coat and took out the satellite phone.

‘One of the snowmobiles broke down,’ she told whoever answered. ‘And Hagger’s dead.’

She waited, fingers drumming impatiently.

‘Have you got a fix on our position?’

Evidently they had.

‘We’ll stay here. I’m switching off the phone to save battery.’

She tucked the phone back in her coat and starting pulling equipment off my sledge. I stood there, helpless, feeling the warmth leaching out of me.

‘Can’t we both go on your snowmobile?’

‘It can’t carry both of us and two sleds. Two people, one snowmobile and no emergency gear isn’t a good equation.’

‘So what’s going to happen?’

‘We’ll put up the tent.’ She undid the bag and pulled out a large red tent roll. Another blast of wind almost blew it out of her hands.

‘Is it safe?’

She didn’t bother to answer. We laid the tent flat on the ground and weighted it with blocks of ice and steel canisters. Several times, we nearly lost it as we raised the poles. At last, we were able to crawl in. We spread mats and sleeping bags; I massaged my jaw, trying to get feeling back.

Greta lit the stove and reboiled water from one of the Thermoses. She pulled out two orange food sachets and offered them to me.

‘Chicken or fish?’

I chose chicken. Copying her, I ripped off the top and poured boiling water over the dehydrated meal. I was too hungry to wait for it to absorb: I shovelled it in too quickly, spilling it on myself like Luke did when he was a baby. Hard fragments caught in my throat. The rush of calories made me shake.

‘No hurry,’ Greta said. ‘Too much wind for the helicopter. They won’t come here for hours.’

‘Are we going to make it?’

I could feel my chest tightening with panic. The more I fought it, the more it pushed back. Forty-eight hours ago, I’d been at home with Luke. Now I was trapped in a tent on a glacier, the wind rising, with a broken snowmobile and a dead body outside. And I was so cold.

Greta didn’t offer any sympathy. ‘This is a Scott tent.’

‘Is that supposed to be reassuring?’

‘Scott survived eight days in one of these.’

‘I thought the point was he didn’t survive.’

‘That was on the ninth day.’

I scratched around at the bottom of my carton, trying to pick out the last bits of food. Without asking, Greta handed me another.

‘Where are you from?’ I asked, as I waited for the second serving to go soft.

‘All over.’

I wasn’t going to let her off so easily. ‘You have to come from somewhere.’

She thought about that. ‘My mother’s Norwegian.’

That explains the looks, I thought. I almost said it, but chickened out. It would be a long wait in that tent if she took it the wrong way.

‘What brought you to Zodiac?’

She rolled over on her side. ‘I need some sleep.’

‘Me too. But I’m not tired.’

‘I’m kind of upset about Martin right now.’

‘Of course.’ I felt like a heel. The truth is, Hagger had made such a fleeting cameo in my life it was hard to remember he’d been there at all. In the blink of an eye, he’d gone from an email on a screen to a bundle on a sledge; I’d never even spoken to him. Whatever reason he’d had for bringing me there, I’d never find out now.

I stared at the roof of the tent. Ice crystals were beginning to form on the underside of the canvas. ‘He was like a father to me.’ I saw the look Greta gave me. ‘For a while.’

It sounded phoney, even to me. But it was true. The memory surprised me, like an embarrassing shirt found at the back of the wardrobe — something to make you wonder who you ever were.

‘As undergraduates, we were all in awe of him. So many stories went round. He was like Professor Challenger, or Indiana Jones. He overwintered in the Arctic on a wooden boat, collecting samples. They said he shot a polar bear and ate his own shoes.

‘The polar-bear story’s not true,’ Greta said.

It occurred to me that we weren’t talking about the same man. For me, Hagger was something from the past — a piece in a jigsaw I’d abandoned a long time ago. For Greta, he was now. Someone she passed in the corridor, ate with in the canteen, sat next to at their movie nights. No wonder she was taking it harder than me.

‘I should have kept in touch. He was an amazing scientist. He—’

She’d stopped paying attention — still listening, but not to me. She was staring at the tent door.

I reached for the rifle. ‘Is it a bear?’

She shook her head and took the gun.

‘It sounds like an engine.’

I heard it too. Deeper than a snowmobile’s gadfly whine — more bass, throbbing beneath the howling wind. The ice beneath us shook. Greta pulled on her boots and unzipped the tent.

The noise stopped. The shaking stopped. I heard the styrofoam squeak of footsteps crossing the snow, the crust snapping. Then that stopped, too — right outside our tent.

‘It’s triple-A,’ an American-accented voice said. ‘You want a lift?’

A yellow Sno-Cat sat parked outside our tent. Not like the machine I’d seen at Zodiac, a relic of the 1960s; this one was low and shiny and powerful and very much of the twenty-first century. Even the snow blown over its door sills looked like it had been styled for the brochure. Three pairs of skis stuck out of a rack on the back, and three men in yellow parkas stood peering at our tent. The word ‘DAR-X’ was stencilled liberally on everything I could see: doors, coats, hats, skis.

‘Trouble?’ Even right there, the man outside the tent had to shout over the wind.

Greta nodded.

He gestured to his Sno-Cat. ‘You want out?’

The tent we’d raised so laboriously came down in a hurry. We left it with the snowmobiles. Hagger came with us on his sledge, wagging behind the Sno-Cat like a tin can tied to a car. I glanced out the rear window, and thought what a strange last journey it was for him.