The notebooks had vanished. You could see the place where they’d been — the only clear space in the lab — but the notebooks weren’t there. Instead, just a single Erlenmeyer flask, placed very deliberately, as though the empty space had bothered someone.

Who could have moved the notebooks so quickly?

I turned on Hagger’s computer. Another antique: it took almost a minute for the logon window to appear. The cursor winked at me and waited for a password.

I didn’t know the password. Did anyone?

Frustrated twice over, I turned to the rest of the lab. I rummaged through the drawers and the cabinets. I even looked in the fridge. It was full of water samples in sealed bags, each labelled with codes I didn’t understand. In the freezer compartment, I found a foot-long tube of ice wrapped in a plastic bag with a reference number scrawled on it in black marker.

I supposed the lab would have to be cleared out, ready for the next occupant. At least it was something to do. I found some boxes and started to lay them out on the floor.

‘This is bullshit.’

I jumped; I hadn’t heard her come in. Greta shut the door behind her, though there was hardly room for both of us with the boxes. She looked furious.

‘I thought … if anyone should do it, it should be me,’ I said weakly.

‘Quam wants to cover it up,’ she announced.

‘Cover what up?’

‘Martin’s death.’

I didn’t understand. ‘How could he do that?’

‘Because he’s scared. He’s base commander, it’s his responsibility. Hagger should have had a buddy with him.’

It seemed tough to blame Quam because Annabel and Hagger had broken the rules. ‘Hagger’s an internationally renowned scientist,’ I said. ‘Quam can’t pretend it didn’t happen.’

‘He’ll say it was an accident.’

‘It was an accident.’

Greta gave me one of her impenetrable looks. ‘Now you sound like Quam.’

I sat down on Hagger’s stool. I was still short on sleep; my head hurt. ‘Can you … explain?’

‘Martin didn’t walk into that crevasse by accident. He knew it was there. He’d rigged the ropes.’

‘He could have tripped.’

‘He was lying on his back.’

‘Maybe the ice broke.’

‘And where was his gun?’

I shook my head. ‘I didn’t see it.’

‘At the bottom of the hole. Not slung on his back. He must have been holding it when he fell.’

Suddenly, everything fell into place. ‘A polar bear. That’s why he had the gun out. The bear advanced, Martin stepped back — and fell into the crevasse.’

Greta’s face hardened. ‘That’s Quam’s theory.’

‘What’s wrong with it?’

‘There was no bear.’

‘How do you know?’

‘No tracks.’

‘Are you sure? They’d be easy to miss.’ I picked up a glass pipette from the counter and turned it over in my fingers. ‘Everything was such a panic.’ Not, I had to admit, that she’d been panicking.

‘The first thing you look for on Utgard is bear tracks. Every time you go out, every time you stop. There were no tracks.’

‘So what do you think happened?’

She looked at me like it was the most obvious thing in the world.

‘Someone pushed him.’

The pipette snapped in my hand. Broken glass scattered on the floor. Blood welled out of the cut that had opened on my finger.

‘Shit.’

I grabbed a wad of paper from the roll near the sink and pressed it to the cut. Blood soaked it almost at once.

‘You should see Doc,’ said Greta.

I threw the paper away and got a fresh piece. ‘It’s … insane. There’s no evidence.’

Greta’s look made me forget about the cut for a moment.

‘You’re the scientist,’ she said as she walked out the door.

‘Wait,’ I said. But she didn’t.

I climbed down from the stool and tried to sweep up the broken glass one-handed. I couldn’t find a dustpan: I had to use a piece of cardboard, trying not to step on the tiny fragments in my socks.

I paused to rearrange the tissue on my finger, and a bead of blood spattered on the floor. I stared at the Rorschach blot it made, wondering what it meant.

I didn’t know anything about Greta. She seemed pretty hard-headed, but that didn’t make her infallible. She’d taken a set of facts, from a confused and horrible situation, and made a leap that couldn’t possibly stand up. In the jargon, she’d confused correlation with causality. Probably because she hated Quam.

Though I didn’t have a better explanation. I didn’t even know why Hagger had brought me there. I glanced over at the counter where his notebooks had stood. They hadn’t come back.

The door opened. To my surprise, it was Greta again.

‘I’m going to get the snowmobile you broke,’ she announced.

Somehow, I’d been around her long enough to understand that this was an invitation.

The winds had dropped. Jensen, the pilot, flew us out in the helicopter. Greta rode up front; I sat in the back with a pile of what looked like Titanic-era life preservers wrapped up in a cargo net.

‘Terrible thing about Hagger,’ said Jensen over the intercom in my helmet.

‘Yeah,’ I heard Greta agree.

‘Tragic accident.’

I waited for her to launch into her murder theory. Thankfully, she kept it to herself.

‘What were you doing yesterday?’ I asked, trying not to make it sound like I was implying anything.

‘Chasing bears,’ said Jensen. ‘Ash was tagging.’

It took me a moment to make sense of that. I assumed Ash must be Ashcliffe, the polar-bear man who looked like Father Christmas.

‘How do you tag a polar bear?’

‘You shoot it with a tranquilliser dart,’ said Jensen. ‘If that doesn’t work, you shoot it again. And make sure you’re out of there before it wakes up.’

‘Get many?’ said Greta.

‘Three.’ A gust shook the helicopter; Jensen broke off to concentrate on the controls. Below, I saw the peaks sticking out of the ice cap like the funnels of sunken ships.

‘Any up near the Helbreen?’ Greta asked.

A defensive note came into Jensen’s voice. Maybe I imagined it. ‘Nope.’

‘Tom thinks Martin could have been chased by a bear.’

‘Maybe you saw it,’ I chipped in.

‘We were further over. Not many bears that far north at the moment.’

I found it odd discussing the bears so casually. To me, never having seen one, we might as well have been talking about dinosaurs.

‘That took most of the day?’ said Greta.

‘Pretty much. We kept trying for one more. Ash buys me a beer if we get four.’

Greta peered through the canopy. ‘We’re getting close.’

Jensen left us in a flurry of rotors and whipped cold air. When the snow settled, it was just me and Greta, two snowmobiles and a sledge. Greta had brought some spare parts. I held open the snowmobile’s nose while she knelt over it and performed surgery. As ever, the moment you stopped moving, the cold started to chip away at you. I pulled my neck-warmer up over my nose. The snow and ice stretched towards the horizon, rippled channels like a dried-up seabed. A desolate place.

‘It’s lucky the DAR-X people were around to pick us up,’ I said.

‘Mm.’ Greta pulled out a piece of the engine. Oil stained the snow green. ‘Lucky.’

There was an implication there, but I ignored it. The place was lonely enough without entertaining the nonsense that someone had killed Hagger in cold blood.

‘Martin visited Echo Bay a couple of times,’ Greta said suddenly.

That surprised me. ‘How come?’

‘He didn’t say.’

Another conversation died before it started. But it made me think of something else.

‘How well did you know him?’

Greta unscrewed a Thermos and poured hot water over the engine. Steam hissed off the cold metal. ‘Can you pass me the five-eighths-inch spanner.’

‘You were good friends?’

‘That’s the three-quarter-inch. Read the number on the handle.’