Grant regarded him with undisguised irritation; she seemed genuinely reluctant to be drawn on the subject. But she wasn’t prepared to let this scenario go unchallenged. ‘Maybe you could explain the sheer number of genetic changes with a strong enough chemical mutagen, but the pattern still doesn’t make sense. Given everything else we’ve seen, some proportion of the animals who escaped from this hypothetical island should have had at least a couple of neutral alterations: changes to their anatomy or biochemistry that wouldn’t kill them or significantly disadvantage them, but which served no useful function at all. So far no one’s seen anything of the kind.’

‘Yes, but even the most “insignificant” disadvantage could be serious dead weight if you have to travel hundreds of kilometres just to be noticed. Maybe we’re only seeing mutants with changes that have been positively beneficial. I mean, you’d have to be pretty fit to fly all the way to Ambon from any of the remote islands in the south.’

Grant gave him an odd look. ‘They found a mutant tree frog in Ceram. That couldn’t have come from too far south—assuming it wasn’t hatched on the spot, which it might well have been.’ Ceram was a large island just ten kilometres north of Ambon. It was heavily populated around the coast, and parts of the interior had been logged and mined, but a considerable amount of rainforest remained intact. If Grant got it into her head to veer north and start traipsing through the jungles of Ceram, he’d never get anywhere near Madhusree’s expedition.

‘There are ferries running between the major islands,’ Prabir reminded her. ‘Something like a tree frog could have hidden in a crate of fruit, or even got on board a plane. Human transport can always complicate things to some degree.’

‘That’s true. But what makes you so sure that these animals have travelled at all?’

Prabir thought carefully before replying. Even if he’d known nothing about Teranesia, wouldn’t it be reasonable to suppose that there was an epicentre somewhere? He said, ‘If they haven’t, their parents or grandparents must have. If you follow the mutations back to their source, every animal must have had at least one ancestor exposed to the same mutagen at some point. I mean, whatever the cause, isn’t it stretching things to think that the same conditions could be repeated in half a dozen different locations?’

Grant shrugged. ‘You’re probably right.’ But she didn’t sound as if she meant it.

Prabir tried to read her face. If the animals weren’t travelling, what was? Any chemical spill severe enough to retain its potency across thousands of square kilometres could hardly have gone undetected this long. A hushed-up nuclear accident was even less plausible.

He said, ‘You think it’s a virus? But if it’s spreading all over the Moluccas, doesn’t that make it a thousand times harder to explain why we’re not seeing any unhealthy mutants? And isn’t it a bit far-fetched to think that it could infect so many different species?’

Grant gave him her sphinx impression. Prabir folded his arms and glowered at her. He wasn’t just killing time now: he was genuinely curious. He’d kept pushing the question aside as a distraction, but what Felix had called his cover story wasn’t entirely false: this was Radha and Rajendra’s life’s work, and part of him really did want to know what they would have discovered if they’d had the chance to complete it.

He said, ‘Unless the two mysteries are one and the same? Unless whatever makes the animals so impossibly successful makes the virus successful too?’

Grant said firmly, ‘We’ll gather some data, and we’ll see what we find. End of discussion. OK?’

Prabir lay on his bunk with his notepad’s headset on, brushing up on his Indonesian vocabulary. It was after midnight, but Grant was apparently still awake and busy. Most of the cabin was hidden from view by the row of lockers alongside the bunk, and the faint glow that diffused around them might have come from nothing but the phosphorescent exit sign, but whenever he took a break from his lessons he could hear the distinctive metallic squeaks of the ‘captain’s chair’. He had no idea what she was doing; with the collision avoidance radar and sonar switched on there was no pressing need for anyone to keep watch.

His concentration was faltering. He froze the audio and took off the headset. The humidity had become almost unbearable; the sleeping bag he was using as a mattress was soaked, and the air was so heavy that it felt as if he was drawing every breath through a straw. Maybe he’d be better off sleeping on deck, now that they were far enough out to sea not to worry about insects. The genetic quirk that had required him to be a walking mosquito killer as a child had no effect on the modern vaccine—another triumph for biotechnology, though when they reached some of the islands with undrained swamps he’d probably wish he still sweated repellent.

He rolled up his sleeping bag and headed for the cabin door. Grant was seated at the console, examining a chart of the Banda Sea stretching all the way down to Timor. Prabir explained what he was doing. ‘Is that OK with you?’

‘Yeah, of course. Go ahead.’ She turned back to the chart. Prabir wondered belatedly if he was eroding her privacy; the cabin windows had no blinds, so the two of them would no longer be as manifestly out of each other’s sight as when he’d been tucked away behind the lockers. But she hadn’t raised any objection, and once she switched off the console she’d be all but invisible anyway.

As he unrolled his sleeping bag on the deck, he tried to decide whether or not he owed it to Grant to tell her he was gay. On one level it seemed like an insult to both of them to suggest that it mattered; unless he’d misread her completely, she was the kind of person who’d start from the assumption that he wouldn’t try to exploit their situation, and she’d certainly shown no sign of wanting to exploit it herself. But he knew that his judgements were sometimes skewed; he was so accustomed to ruling out by fiat the whole idea of sex that he forgot that other people weren’t necessarily viewing him through the same filter. A few years after he’d started at the bank, he’d been assigned two graduate trainees to supervise while they were on a month’s rotation in his department: a man and a woman, both about his own age. He’d done his best to put them at ease, remembering how nervous he’d been in his own first weeks on the job, and as far as he could tell he’d been equally hospitable to both of them. But after they’d moved on, the news had got back to him that the woman had found his behaviour positively oppressive. He’d been too nice. He must have wanted something.

There was a gentle breeze moving across the water; for a minute or two Prabir was almost chilly, until his skin reached a kind of clammy equilibrium. The boat was pitching slightly as it crossed the waves, but that bothered him even less than it had in the confined space of the cabin.

He’d brought his notepad with him, but he was too tired to continue with the language lessons. He stared up at the equatorial sky, the sky he’d seen from the kampung at night: obsidian black, with stars between the stars. He could fix his eyes on one spot and try to map it, but his mind stopped taking in information long before he hit the limits of vision.

A few hours before he’d almost welcomed being back on the Banda Sea, but the connection seemed a thousand times more immediate now, the details of his memory sharper by starlight. He could feel the years melting away in the face of the accumulating evidence: the musical sound of the half-familiar language ringing in his ears, the struggle to sleep on a humid night. That was how memory worked, after all: placing like moments side by side. There was no linear tape inside his head, no date stamp on every mental image. It didn’t matter what had happened since. Nothing could stop the days and nights of eighteen years before becoming like yesterday.