‘Aren’t you curious why we’re doing this?’

She swerved the Sno-Cat around some obstacle I didn’t see.

‘Tell me.’

I explained my hypothesis, how the enzymes were running under the glacier and out into the sea through the mines.

‘The mines are sealed with concrete,’ she pointed out.

‘Water can get in through microscopic cracks.’

‘But how do we get in?’

‘I think Hagger found a way. He used Annabel’s Rhodamine dye to track the water flow under the glacier; he had it on his hands when he died. He must have followed the dye down one of the tunnels …’

‘Moulins,’ Greta corrected me.

‘… and found where the enzymes were coming from.’

A pause. ‘What’s an enzyme?’

I’d spent the last three days thinking about nothing else; the question threw me. But of course, why should she know? I thought for a moment. The throwaway answer wouldn’t do.

‘How much do you know about DNA?’

‘Some.’

Last year, Luke’s school invited me to give a talk about genetics to his Year 3 class. I fell back on that and hoped I didn’t sound patronising.

‘Imagine the human genome like a tower made of Lego bricks. The bricks can only be one of four colours, and the tower is three billion bricks tall. The bricks are stacked in pairs — so six billion in total — but there are certain rules. A red brick always goes next to a white one, and green always next to blue.’

‘OK.’

‘Each pair of bricks is what we call a “base pair”. In reality, the different coloured blocks are amino acids, four chemicals known by their initials G, C, T and A. To “read” the genome — sequence it — you just have to write down all those letters in the right order.’

I glanced across at her. ‘Still with me?’

‘Keeping up.’

‘Now, DNA makes RNA, which is like a copy of that Lego tower but only one block wide. RNA makes molecules called proteins, and proteins — among other things — make enzymes. An enzyme is a tiny biological machine, made of proteins, that performs a specific task. Like a little mobile chemical lab. It can be as fundamental as making your muscles move, and as mundane as breaking down stains on your laundry. You probably have them in your washing powder.’

‘I use non-bio.’

‘If DNA is the operating system of life, enzymes are the apps. The enzyme Martin found coming off the Helbreen is one that’s been created in a laboratory, for making DNA. Put it in a solution with the four bases, and it’ll grab them one after the other and stitch them together.’ I thought of Luke’s bedroom at home. ‘Remember my Lego analogy? Imagine you’ve got Lego bricks scattered all over the floor. The enzyme is like a little robot that can grab them one at a time, and snap them together in a preset order.’

Greta drove on. With the clouds low, it was dark enough that I could see the headlights roaming over the snow in front of us.

‘That’s why we’re going to the glacier?’

‘There’s something else.’ I got out the piece of paper covered in numbers. ‘Eastman intercepted these numbers being transmitted somewhere near Vitangelsk.’

She crunched into the next gear as if she was trying to decapitate it.

‘I know what the numbers mean.’

She didn’t look as impressed as I’d hoped. ‘Is it the password to get into the mine?’

‘It comes back to DNA. You see, the biggest problem with sequencing DNA isn’t the technology, or the process. That hasn’t changed much in thirty years, except to get quicker and cheaper. But each individual’s DNA contains three billion base pairs — that’s three billion pieces of information. And if you’re going to make use of it, you have to store it accurately and be able to retrieve it. Even one mistake, out of three billion, could mean the difference between perfect health and an incurable disease.

‘And the actual sequence makes mistakes too easy. In the genome, there are long stretches where the same base pairs, or pattern of bases, repeat themselves. Coming back to the tower, it’s as if you’re told to put 297 red bricks in a row. Very easy to miscount.

‘The man I did my doctorate with — Richie Pharaoh — he was obsessed with this problem. Any time you sequence DNA, you’re working with margins of error. You have to decide what you think’s acceptable. When the original Human Genome Project announced to the world that they’d sequenced the whole human genome — the articles in Nature and Time, the TV fanfare, the ceremony with Bill Clinton — what they didn’t say is that one in ten thousand of the base pairs was probably wrong. That was the margin of error they’d agreed on.

‘Now, one in ten thousand probably sounds pretty good. But with three billion base pairs, that’s still three hundred thousand mistakes — and it only takes one to ruin someone’s life. And there are two ways errors can creep in. Either when you’re reading the sequence, or when you’re writing it down. Which, practically, means on a computer.

‘So Richie Pharaoh devised a solution. Instead of standard binary code, the noughts and ones, where the same number always stands for the same base letter, he created a more advanced code where there are three numbers — zero, one and two — but each one records a different value depending on what went before it. Sort of like the Enigma machine in the Second World War, where the next letter changed depending on what letter you’d just typed.’

The system was pure Richie. Subtle and slippery, a solution to a problem most people, even leaders in the field, hadn’t realised existed yet.

Greta looked mystified. ‘Is this going to be on the test?’

‘The point is, Pharaoh never published it and it never caught on. Scientists were happy with the fiction that they’d “done it”, the software got better at correcting errors, and every time he tried to explain it to someone, their eyes glazed over. No one used it — except Richie Pharaoh. He always used it for his own experiments.’

‘And now it’s on Utgard.’

‘I’m wondering …’ I took a deep breath. What I was proposing was so ludicrous, my mind hit the buffers every time I tried to assemble the thought.

‘I’m wondering if the reason Martin brought me here was because of Richie Pharaoh.’

Forty-six

‘I should probably tell you some things about Pharaoh.’

We were up on the ice dome. A dream landscape of soft peaks and hard snow, and hidden fissures waiting to swallow you. A landscape like the past.

‘At university, Richie Pharaoh was a racing driver in a world of traffic wardens.’ Literally: his red NSX stood out a mile against the grey Volvos and Priuses in the car park. ‘He was American, a New Yorker, smarter than everyone and arrogant as hell, but the arrogance only made you try harder to impress him. All the grad students wanted his attention. You knew if you made it in his lab, you could walk into any job in the country.

‘But before he came, I’d started my PhD with Martin. That was where I met Louise. She was smart, pretty and ambitious. We worked hard, we played hard, we had a lot in common. Soon, we fell in love.’

Like a lot of stories, it sounds easy when you tell it back. I’d had a few girlfriends at university, but I still wasn’t confident. Louise seemed so cool and unattainable. It felt like an eternity — really, it was only a few weeks — before I plucked up my courage and asked her out. Afterwards, she admitted she only said yes because she was so sure I hated her. Apparently, I look ferocious when I’m concentrating.

‘I said we worked hard. Unfortunately, the work in Martin’s lab was tedious as hell. Endless cycles of heating and cooling, freezing and melting, measuring tiny fragments of amino acids to see if they’d grown at all. Martin had a great story to tell about how he was going to upend the scientific consensus, make us famous and answer the greatest mystery of all — the origins of life. That was why we came. The problem was, the science didn’t agree with him. After a year, it looked as if I wouldn’t have a single positive result to write up in my thesis. Which didn’t have to be the end of the world: you can publish a thesis on negative results. But it won’t get you a job afterwards.’