I filed the question under ‘Save for Later’ and found the right spanner. ‘Did he ever say why he brought me here?’

‘He thought you could explain something. “Tom Anderson will know,” he said.’

‘What does that mean? Know what?’

‘He wasn’t talking to me.’

‘Who, then?’

‘Himself.’

She pulled the starter cord and the engine exploded back to life. I dropped the nose cone and she latched it shut.

‘You want to go?’ she asked.

‘Where?’

‘The crevasse. It’s only a few kilometres.’

I hesitated.

‘What are you afraid of?’

‘Bears,’ I said, straight-faced.

The crevasse looked different now. In the twilight that passed for night, it had been a dull grey hole. Today, in the sunshine, it came alive. The walls glowed a cool blue, like a swimming pool sparkling in the light. Greta held me a few metres back.

‘Do you see any bear prints?’

‘I wouldn’t know what to look for.’

She took off her glove and pressed the heel of her hand into the snow, making a rounded kidney shape. Spreading her fingers, she poked five holes just in front of it for the toes.

‘That. But bigger, like a soup plate.’

I didn’t see any. ‘Couldn’t the wind have covered them?’

‘You see your prints?’

I did. Softened by the wind and half filled with blown snow, but still clear enough from the day before.

‘A bear weighs up to a thousand kilos. He makes a deeper print than you.’

I did a slow scan of the snow, right the way around Hagger’s safe area.

‘Point taken.’

Greta advanced to the crevasse. I followed — and almost walked straight into a hole. Not a natural hole: an almost perfect cube cut out of the snow and ice, straight-sided, flat-bottomed, about a metre and a half deep. I’d seen it the day before, with a shovel standing next to it. The shovel had blown over in the night.

‘What’s that?’

Greta barely looked at it. ‘Snow pit. To measure layers in the glacier.’

‘Martin’s work was on sea ice, not glaciers.’ Notwithstanding the glacier core I’d seen in the freezer in his lab.

‘He said he’d come to get samples.’

‘Isn’t there a glaciologist at Zodiac who does that?’

‘Dr Kobayashi.’

I remembered her. Annabel, the only other woman on base. Slimmer, taller and — some would say — more attractive than Greta. Perhaps that explained the sourness that had crept into Greta’s voice.

Greta knelt and scrabbled in the loose snow, about ten feet back from the crevasse. Her hand came up holding a black mitten.

‘He dropped his gloves.’

‘Why?’

‘Stand here,’ Greta told me, pointing at a spot on the ground next to where she’d found the mitten. ‘Now take a step back.’

Feeling silly, I did what she told me.

‘You see your footprints.’

‘Yes.’

‘And the ones next to it?’

Now that she said it, I did. Side by side with mine, softened by the wind and slightly longer.

‘Those are Hagger’s.’

I took her word for it.

‘What do you see?’

Even with the outline eroded, I could make out the heel and the toe. Pointing the opposite way to me.

‘He walked away from the cliff.’

Greta gave an impatient sigh. ‘Really?’

I thought about it for a moment — and reached the obvious conclusion. ‘He was walking backwards.’

‘You think it’s a good idea to walk backwards in a crevasse field?’

‘He would have had to go backwards to climb down into the crevasse.’

‘Yeah,’ she agreed. ‘Except he wasn’t clipped on to the rope.’

Greta walked to the edge. ‘Martin was roping up. He put the harness on. Then someone came. They threatened him. Martin backed off; he was scared enough to get out his gun. He took off his gloves so he could pull the trigger. But he’d gone too far.’

I came up beside her and looked down into the crevasse. At the bottom, I could just see the impression in the snow where Hagger had landed. The abandoned rifle lay a few feet away.

Had he really been chased to his death by someone from Zodiac?

‘It’s too sick to think about,’ I said out loud.

Greta’s look made me cringe.

‘Is that what they taught you in science school? Don’t ask difficult questions?’

‘I don’t even know what questions I’m supposed to ask.’

She started to walk back to the snowmobile. ‘Who’s got big feet?’ she called over her shoulder.

‘What’s that supposed to mean?’

She stopped and pointed. In a clean patch of snow, I could see another set of footprints. Bigger than mine; bigger than Hagger’s. They tracked Hagger towards the crevasse — then stopped, a couple of metres back from the edge. Probably about the time Hagger realised there was nothing under him but air.

‘Who’s got big feet?’ I repeated. I traced the tracks in the snow, wondering how far they’d lead me. About ten metres, where a jumble of broken rocks marked the edge of the glacier. Another dead end.

I put my hand in my pocket and felt a lump, the key I’d found by the edge of the crevasse. I took it out for Greta to see and explained where I’d found it.

‘It must have fallen out of Martin’s pocket, I suppose.’

‘I never saw him with a key.’

‘How else—’

She pointed to the large footprints. ‘Maybe his.’

That was a nasty thought. I dangled it away from me, like something picked out of a blocked drain. No clue to say who it might have belonged to. I ♥ NY didn’t mean much. I mean, who hasn’t been to New York?

I put it away and looked back at the footprints.

‘Shouldn’t we take some photographs? Something to show Quam?’

‘You trust Quam?’ Greta had got her backpack off the snowmobile seat and zipped it open. She pulled out a fat coil of rope and a webbing harness, which she tossed to me.

‘What’s this for?’

She shook out the rope and tied it around the snowmobile’s cowling. She handed me the other end and nodded to the crevasse.

I backed away. ‘I’ve never done anything like this.’

‘Then you should learn.’ She snapped a carabiner at me like a crab’s claw. ‘If something happens, you need me up top to get you out.’

The light changed as she lowered me in, like slipping into a lagoon. An intense, sapphire blue that soothed my eyes after the stark white landscape. I couldn’t stop looking at it. The ice walls swam in sinuous shapes, curves and hollows that no human mind could have conceived.

I shuddered as my feet touched down on the snow at the bottom. For a moment, I felt very clearly that I was standing in Hagger’s grave. My senses came alive, fluid roared in my ears and the ice seemed to tremble, as if the walls were colliding to crush me.

Greta’s face appeared above me. Small, a long way off.

‘Are you OK?’

‘Fine.’ I put out my arm and pressed my gloved hand against the wall, just to be sure. The ice was cool and adamant. One day, it would move and close up Hagger’s grave. But not now.

I walked along the crevasse floor, the rope paying out behind me. It wasn’t long, maybe twenty or thirty metres, curving in a shallow crescent so that from one end you couldn’t see the other. The only marks in the snow were my own footprints. Whatever Hagger had planned to find here, he hadn’t had a chance to look.

They call Utgard the last place on earth. For me, buried in ice, freezing cold, at the end of a crevasse where a man had died, I felt like the last man on earth. The blue walls no longer bathed me: they drowned me. There was nothing here.

But as I turned to go back, something caught my eye. A strange formation at the bottom of the cliff, flat grey against the blue-gloss ice. Spindly columns poking out of the snow like the teeth of a comb. Ivory smooth. I reached out to touch them.

And gasped as I realised what they were. The sound echoed off the ice, back and forth, as if I was in the throat of an enormous beast.

A beast who ate bones. That was what they were. Bones. I saw it the moment I touched them. Limbs and a ribcage, so small that for a ghastly moment I thought it might be a child’s. Then I got hold of my senses.