To tell the truth, I hadn’t got very far. To leak the data, you’d have to understand it, and the climate expert at Zodiac was Fridge Torell. Well, he’s the biggest global-warming fanatic there is: Greenpeace, Friends of the Earth, WWF, he carries so many cards they don’t fit in his wallet. Scientists guard their results like a pot of gold at the best of times. It was inconceivable Fridge would give away his own data to undermine the cause.

Then Martin Hagger died — fell in a crevasse. Tragic. I knew, from some private conversations, that he’d been under pressure with work, things not going his way. I thought it had got too much for him. But then I started to wonder.

I know it sounds ridiculous, that someone would be killed for a few numbers on a graph. But there’s a lot of money chasing round the Arctic. Ice caps are melting; places that have been out of bounds for fifty thousand years are suddenly opening up. Just when we thought we had the planet all parcelled out, it turns out there’s a bit more to grab. People get foolish when they think they can have something for nothing. And if fools and money are involved, anything can happen.

Hagger had an assistant, fellow named Tom Anderson. Quiet, gentle and desperately unlucky: he landed at Zodiac the day Hagger died. I spoke to him once or twice, liked him at the time. There was a sorrow in him, but dignified, you know? Life had dealt him a rough hand, and he was trying to play it the best he could. He was supposed to have gone home already, but the plane got delayed — often happens — so he went up to spend the day at Camp Gemini, on the ice dome. Then Annabel Kobayashi and Jensen the pilot carried him into my medical room on a stretcher. He was out cold.

‘He fell in a moulin,’ Dr Kobayashi explained.

Well, you couldn’t make it up. First Hagger, now his assistant. A moulin — perhaps you know this, Captain? — is a hole in the glacier that the meltwater bores out in summer. They tunnel under the ice; some of them go on for miles. Anderson did better than his boss — he was alive, at least — but he’d banged his head hard. I gave him Mannitol to ease the swelling, and put him on halothane to keep him under.

‘Is he going to make it?’ Jensen asked.

There was no point lying. ‘You can’t tell with head injuries. He could be right as rain tomorrow morning — or he might never wake up.’

Of course, I wondered if it could be coincidence. ‘What happened?’

‘Didn’t see,’ Annabel said. ‘I’d gone for a wee behind the moraine. When I came back, he wasn’t there. I found him at the bottom of a moulin. Stupid,’ she added fiercely. ‘He shouldn’t have left the safe area. I marked all the moulins at the end of last season. Martin must have taken the pole down.’

The emotion surprised me. Annabel wasn’t what you’d call a demonstrative person. Around Zodiac, they called her the Ice Queen. If she’d been shaken up, I didn’t like to think how the others were taking it.

The doctor at Zodiac has a tricky role. He’s confessor, counsellor, friend — and psychologist. If people start cracking up, it’s his job to nip it in the bud. It happens more often than you’d think. Or perhaps you think it would happen all the time in a place like Zodiac.

Annabel slipped a bag off her shoulder, a standard-issue Zodiac field pack. She unzipped it and took out a green notebook, with a sheet of paper pressed between the pages. It was damp and creased and made no sense at all. Just a page full of numbers — zeros, ones and twos, like some kind of Sudoku for idiots.

‘This was Hagger’s. Anderson found it in a snow pit just before he fell.’

‘Did he say what was so important?’

‘No.’

I glanced through the rest of the notebook. ‘You’d best leave this here.’

‘I think—’

‘Obviously it meant something to Anderson. If I put it where he can see it, it might help him come round.’

Annabel gave me a look — but we doctors are trained to sound convincing. It might even have been true. A head injury’s a funny thing, poorly understood.

I shooed the others out of my office. Once I’d satisfied myself Anderson’s condition was stable, I turned my attention to the notebook. An idea had struck me, and was building nicely into a theory. There hadn’t been a fatal accident at Zodiac in twenty years. Now we’d nearly had two in three days: Hagger and his assistant. It couldn’t be coincidence. I’d seen Anderson poking around Hagger’s lab. I wondered what he’d found. Or been trying to hide.

And if you started to think about it, you might ask a few more questions about Anderson. Starting with how he came to be at Zodiac in the first place. Most personnel are selected a year in advance, there’s rigorous screening and months of training. Anderson swanned in on forty-eight hours’ notice, didn’t even bring a proper coat. The story they put about was he’d come to replace Hagger’s old assistant, South African fellow named Kevin, who’d had to go home with a wisdom-tooth infection. But the doctor at Zodiac is also the dentist, and I can tell you that boy’s teeth were sound as a drum. The truth is, Hagger decided he wanted Anderson, and when Quam said he didn’t have funding for two assistants, he packed off the unfortunate Kevin and replaced him. So you could say I was curious to see what Hagger had in his notebook.

Unfortunately, I couldn’t make head nor tail of it. Lots of numbers, some equations and pretty graphs, and precious few words to explain what they might be. Lots of cryptic little notes like Check SO ions and Concentration of X and Where is X coming from? A hand-drawn map of Utgard scattered with little x’s like a treasure map.

But there were a few sentences I could read. And one of them made me very anxious to talk to Fridge Torell.

I found him up a mast on the edge of the base, cracking ice off some instruments as he hung on to the steel frame. It’s tricky work: if your skin touches the metal, it bonds like cement. Most scientists would leave it to their students, or the techs, but Fridge is a hands-on sort of fellow.

‘I need to ask you something,’ I called up. ‘About Hagger.’

An icicle, two feet long and sharp as a knife, dropped off the mast and stuck quivering in the snow. I took a step back.

Fridge clambered down and dropped the last few feet on to the snow.

‘Nothing works in this fucking place,’ he complained.

‘Data link down again?’

‘It’s up — but all I’m getting is garbage.’ He made karate-chopping motions with his hands to get the circulation going. ‘Some kind of interference screwing with it.’

I showed him the notebook. ‘Anderson found this. It belonged to Hagger.’

He shouldered the rifle he’d left leaning against the base of the tower. ‘Can’t Anderson help you?’

‘Anderson’s in a coma.’

‘Shit. How did that happen?’

I told him. ‘The last thing he did was find this notebook. I thought there might be something in it that could explain why Hagger died.’

I could tell the kind of look Fridge was giving me from behind his sunglasses. ‘Quam said it was a polar bear.’

‘There are different theories about that,’ I said, non-committally.

‘So what do you want to know?’

‘Can we go somewhere private?’

He thought a minute, then nodded to a hut near the flag line. ‘How about Star Command?’

Star Command was one of those prefab red pods that we used all over the place at Zodiac. This one was fitted with a sliding roof, and a Buzz Lightyear figure nailed above the door. Someone had stretched out his arms so that he approximated a crucifix. In winter, the caboose housed telescopes and aurora cameras — hence the name. With summer coming on, the telescopes had been packed away and the caboose was empty. Or should have been.

Fridge kicked open the door and stuck his head in. ‘Who put these here?’

Three machines sat on a table against the far wall. From a distance, they looked like fancy photocopiers. I went over and wiped a layer of frost off the front of one.