Another thought. I looked at the sample bags, thinking hard. The ones I’d used for the beakers were already half empty — if I did it again, there’d be none left for future experiments. I dithered for a moment. Using it all up felt like stealing from a dead man.

Hagger’s gone, I told myself. If he was lucky, he’d get a small plaque in the mess, maybe a photograph on the wall with the other ghosts. The samples would get tipped down the sink if I didn’t use them.

I emptied the two bags and repeated the experiment — three beakers, three samples, 10ml of Echo Bay water in each — but this time I cut three pieces off one of the pipes, and dropped them in. They bobbed about on the surface, like the last remnants of a shipwreck.

The voice over my shoulder made me jump. ‘All staff, please report to the mess for an urgent briefing.’

The gist of the meeting was that everyone’s confined to base. Quam blamed the inevitable Health and Safety. It’s fair to say the staff aren’t happy: Eastman, in particular, gave Quam a hard time. I slouched in my seat and tried not to get blamed.

Afterwards, Eastman came to visit me. No particular reason; I wonder what he wanted to know. I don’t trust him. If I had to pick anyone at Zodiac who I thought might be capable of murder, it would be him. Superficially, he’s got that all-American charm: energetic, engaging and very good teeth. But if you look at the eyes, there’s something dead, as if there’s a small man inside his head pulling levers to operate the smile.

He asked how I was doing. It’s getting tedious answering that question — I feel like an elderly aunt who’s had a fall. I suppose I should be grateful for the sympathy. Then he asked about my work. Flipped through the notebook, which I didn’t like, and found the sheet of paper that nearly killed me chasing after it in the wind. The one with the strange noughts, ones and twos.

‘It’s mine,’ Eastman said.

That was news. But he didn’t know any more than that; it’s just some piece of radio garbage he picked up interfering with the instruments. Nothing to do with anything Hagger was working on.

‘Nothing about DAR-X in the notebook?’

I told him that Hagger had taken some samples at Echo Bay.

‘He ever do any work at Vitangelsk?’

‘Not that I know of.’

‘How about that key?’

Eastman’s like that: always moving on. I’m sure when he was a kid they stuffed him full of Ritalin. I told him how I’d found the key at the crevasse, not mentioning Greta’s theory that it came from Hagger’s killer. He made a joke about Hagger’s liquor cabinet, which I laughed at dutifully, but I didn’t like the way he looked at the key. I’d have locked it away if I could — but, of course, I couldn’t. Ironic. I hid it as best I could in a drawer full of lab equipment as soon as he’d gone. Then I took a sample from each of my beakers, strained them and stained them and put them under the microscope.

The green sample and tap water showed no change. But in the red sample — and especially the red sample with the piece of pipe — you could see even without counting that there were more bugs in the water than there were two hours ago.

I looked at the graph in Hagger’s notebook again. Apparently, this should be just the beginning.

I’m writing this by torchlight, burrowed down in my sleeping bag like a boy reading past his bedtime. Except it’s not kids’ games any more. There’s a storm raging outside so fierce it ripped off the anemometer; I think our communications dish has gone too. It sounds as though the whole Platform might blow away.

I’m not on the Platform. I’ve shut myself in the caboose they call Star Command. It sounds melodramatic, but I can’t take any more risks.

Another gust of wind. The caboose is one of those round domes, like a diver’s helmet; it’s anchored into the ice, so it ought to be secure. But that wind … I can imagine it picking up the whole island and dropping us somewhere in Mongolia.

The key was gone this morning. I suspect Eastman, from the way he was looking at it yesterday. A horrible thought: what if it’s his? What if he was the one who dropped it by the crevasse? Maybe he came back for it Monday afternoon, and hit me on the head while Annabel’s back was turned?

I went to confront him, but I couldn’t find him anywhere, even with everyone confined to base. I asked Quam, who said he hadn’t seen him. He wouldn’t meet my eye as he said it.

First the notebooks, now the key. Whatever Hagger was on to, someone at Zodiac is after it.

But they didn’t touch the samples. I know, because I shut them in the fumes cupboard, with a strand of hair jammed in the door that would fall out if anyone opened it. Silly stuff I got from a spy novel. Hard to believe it’s real life.

First thing this morning, I got out the beakers and examined them. Even without the microscope, the results were startling. In the green samples and the tap water, no change. But the red sample without the pipe was cloudy, and the one with the pipe in it looked like milk of magnesia.

I lifted out the pipe fragment with a pair of tweezers. The yellow plastic had turned brown, the smooth surface pitted and eroded. The sides were smeared with a translucent white sludge that, under the microscope, turned into a writhing mass of tiny worms, feasting on the pipe like maggots on old meat.

I put it back in the beaker so they could continue their meal in peace.

‘Bon appétit,’ I said to them.

‘Talking to your experiments is the second sign of madness,’ said Greta behind me. I jumped.

‘What’s the first?’

She snorted, as if it was obvious. ‘Coming to Zodiac.’

She glanced at the row of beakers, but didn’t ask what I was doing.

‘I think I’ve made a breakthrough,’ I told her.

She didn’t look impressed.

‘DAR-X were having a problem with corrosion on their pipes. Martin went to Echo Bay to take a look, as a favour.’ I slipped the sample under the microscope and beckoned her over. ‘See what he found?’

She bent over it stiffly, like someone peering over the edge of a cliff.

‘Worms.’

‘Micro-organisms, feeding on the pipes from the drill rig. Methane was seeping out; that’s why Fridge got abnormal readings. But Martin wasn’t interested in the bugs. He wanted to know why they were growing there.’

She looked up from the microscope.

‘Can bugs really eat plastic?’

I nodded. ‘You’ve seen plastic burn? As a rule of thumb, anything that burns has energy in it, and plastic is incredibly rich. It’s made from petroleum, after all. These bacteria can metabolise that into food energy.’

‘Smart.’

‘But there’s something else in the water, something helping them reproduce.’ I paused. ‘Something that’s making all the sea life on that coast explode, from plankton to polar bears.’

‘So what is it?’

I deflated. ‘I don’t know. I don’t even know where it came from. It just pops up in the Helbreensfjord, as if by magic, then floats away on the Stokke current.’

‘The glacier?’

‘That would be the obvious candidate. But Martin tested it from top to bottom and couldn’t find a trace.’ I thought of all the green-ringed X’s on the map. ‘That’s what he was doing the day he died.’

‘Did he know what it was?’

I spread the notebook open on the bench and turned through it. ‘I think so. Look here.’

It was one of the last pages he’d written on. Another list of the samples (I know the references by heart, now) — with a set of numbers against each one.

‘What does “ppm” mean?’ Greta asked, reading one of the headings.

‘Parts per million. It’s a measurement of concentration.’

She pointed to the numbers. ‘Is it a lot?’

‘Depends on what it’s referring to. If you’re talking nitric acid, twenty-five parts per million is bad news. Something like ammonia, two or three hundred wouldn’t do you much harm.’