Hagger had obviously had plenty of opportunity to give information to DAR-X. From what I knew of his work, it involved plenty of chemistry, so he surely could have understood the data. And then DAR-X had been near the Helbreen glacier, probably the only people at that end of the island, when he died.

That still didn’t explain how they could have got to Anderson. But all I had for what happened to him was Annabel’s word. Annabel and Hagger had been close — that was common knowledge. And she should have been his partner the day he died. Could they both have been in on it?

I worked on the theory. Annabel and Hagger had been passing secrets to DAR-X — but then he got cold feet and wanted to stop. That was why she’d been so cross with him when she came back this season. The two of them went to the Helbreen to rendezvous with DAR-X, he threatened to expose them, and she pushed him into the crevasse. Then took out Anderson for good measure.

I didn’t want it to be true. I didn’t want to think the worst of them. But that’s the problem with Zodiac. All the thoughts that anchor you in real life, the routines and the friendships, go out the window. Nature abhors a vacuum: something has to evolve to fill the gap. And often it isn’t very nice.

We had one stop to make on the way home. There’s an old hut at Seal Point, about sixty kilometres up the coast from Zodiac on the east side. They built it in 1953 for the International Polar Year; four unlucky scientists spent thirteen months there recording the weather. Legend has it when the relief party came, three of them were living in an igloo eating seal meat, and one was holed up in the cabin with his rifle.

After that, the hut was abandoned. But a few years ago, the base commander of the day decided to refurbish it as a holiday cottage for scientists who wanted a break. I’ve sent one or two people there myself, when I thought they needed to get off the Platform. It’s a picture-postcard place: little red cabin nestled in a hollow, tin chimney poking out of the roof and snow-capped mountains behind. All that spoils the scene is the barbed wire strung around the windows. You need it to keep out the bears.

We’d come to drop off emergency supplies. Jensen and Eastman left a couple of fuel drums in the cache, while I went inside to check the first-aid box for anything that had expired. It’s a strange feeling, being the first person in a place that hasn’t been touched in months. All the windows were shuttered, though sunlight wormed around the cracks creating a sort of amber twilight. Just the one room. Two bunks on each wall — the lower ones doubled as benches for the table that folded down between them. A tall cast-iron stove, vintage 1953, stood in the corner like one of those Victorian grave markers, next to a cupboard. On the wall, a woman crouched in her bra and knickers and made come-hither eyes at me. She must have been cold, wearing so little. She’d been torn from a magazine, though she still looked good. I think it was Cat Deeley.

A tin of corned beef lay open on the table, spoon lolling inside it, as if someone had been here moments ago and just popped out. I could smell smoke in the air.

I stepped over the threshold — and almost fell on my arse. A thin slick of ice covered the floor. I suppose snow must have blown in, melted when they lit the stove, and then froze again.

I found the medicine box in the cupboard and went through it, checking the contents against the list, filtering the out-of-date stuff. A couple of the morphine bottles were missing, which worried me. Probably an oversight, but I made a note to tell Quam. You don’t want people shooting up out there.

I finished, but the smoke smell still bothered me. The biggest risk at Zodiac is fire. You wouldn’t think it, surrounded by ice and snow, but it’s so dry that once fire takes hold it doesn’t let go. Well, we found that out, as you know.

I opened the stove, just in case. You’re supposed to sweep it out before you go, but this was full of ash. Fine, white and spindly: they’d been burning paper, not coal or wood. They must have left in a hurry. A few fragments hadn’t burned properly.

I reached in. The feathery ashes crumbled under my touch. My hand came out grey with soot, clutching a charred corner of green cardboard. It looked like the cover of the notebook Anderson found up on the glacier.

Fifteen

‘You all set?’

I spun round as if I’d been caught stealing from the church box. It was only Eastman.

‘We’re done with the fuel dump.’ He saw my hand covered in ash. ‘Did you start a fire?’

‘Just checking for safety.’ I clanged the stove door shut. ‘We’d better get back. The plane’ll be coming soon.’

I slipped the cardboard fragment in my coat pocket and hoped Eastman hadn’t seen it. Paranoia was in full flow: I sat tight in the helicopter, silent with my thoughts, while Eastman and Jensen chattered away. Below us, the helicopter’s shadow chased over the frozen ocean, rippling on the bumpy surface. I thought about the vast pressures seething under the ice, crushing and pulling in every direction, and those little wrinkles that were the only outward sign.

The moment we landed, I hurried to the medical room. Anderson lay on the bed, still out, fogging the mask with his breath. I was surprised how relieved I felt. If someone had tried to kill him once, what was to say they wouldn’t try again.

I opened the drawer where I’d put Hagger’s notebook. And — nothing. It sat exactly where I’d left it: green cover, graphs, all the pages. I had to touch it to be sure it was real.

So what got burned?

I compared it to the fragment of green card I’d rescued from the stove. No question, they came from the same batch. Same colour, same thickness.

Hagger might have had more than one notebook. I might even have seen them, lined up against the wall in his lab. I went down and put my head round the door. If there had ever been notebooks there, they were gone now. A big glass flask sat where I remembered them, as if trying to fill the space.

I went to the front door and examined the field log. It was a long shot, and it didn’t come off. No one had helpfully signed out that they were going to the cabin to destroy Hagger’s research. Just the usual comings and goings. The thing with the cabin is, anyone could go there without being noticed. An hour or so by snowmobile, a quick blaze and then home.

As I said before, bad thoughts grow like weeds. Each time the Platform creaked in the wind, I jumped like a schoolgirl. Back in the medical room, I popped a diazepam to calm myself down. I don’t often self-medicate — but I was trembling badly; my heart was threatening to run off with me. I locked the notebook in the cabinet where I keep the hard stuff. I was about to add the piece from the cabin, when something made me give it one last look.

I squinted at it, and as it caught the light I saw tiny indentations. Writing. Grey pencil on green card, hard to make out under the muck from the furnace. I blew off the soot, trying not to smudge it any more, and angled the card to the light.

Does Ash know where it’s going?

‘Is he ready?’

Greta had come in without me noticing. It happened a lot, that sort of thing — it’s how Zodiac was. No locks on the doors, not even the medical room. I looked to see if Greta had seen what I’d been doing. If she had, she didn’t comment. She never gave anything away.

‘Plane’s coming,’ she said. ‘Help me move him?’

We wrapped him up the best we could manage and stretchered him down the steps. The Sno-Cat was waiting, engine running to keep the cab warm. We loaded Anderson in the back; Hagger’s body went strapped to a sled behind it, wrapped up in a body bag I’d found at the back of a cupboard. Greta drove as carefully as she could, but the old beast wasn’t built for a soft ride. A couple of times, I almost had to throw myself on top of Anderson to keep him from hitting the ceiling.