The whole island was low jungle, with soil trapped by dead coral that must have grown on a submerged volcanic peak. They’d barely passed the first palm tree when a cloud of small flies descended on them, biting them relentlessly.

They retreated to the beach. Grant shielded her eyes with one hand as Prabir circled her with the insect repellent. She seemed tense out of all proportion to the inconvenience; he couldn’t even smell the stuff. ‘You’re not allergic to this, are you?’ He checked the can for warnings; if she went into shock he’d have to dash for the medicine cabinet.

‘No. It’s just cold.’

They swapped places, and Prabir quickly discovered that she wasn’t joking; the solvent evaporated so quickly that it was like being doused with a fine spray of ice. He mused, ‘If we engineered ourselves to sweat isopropyl alcohol, humidity would have no effect on the efficiency of the process. What do you think?’ Come the revolution. But the revolution was taking its time.

‘I think you’re completely unhinged.’

They tried the jungle again. The insects retreated, but the undergrowth was even more impenetrable than Bandanaira’s, with a dense, thorned shrub that Prabir had never seen before crammed into the gaps between the familiar ferns. He tore off a spiked, leathery branch and held it up to Grant. ‘What are the thorns for? I know there are plenty of birds that eat fresh shoots, but what is there here that would try to eat something this old and tough?’

Grant frowned. ‘Beats me. As far as I know, all the lizards here are insectivores. You can find deer this far east, but only where they’ve been introduced by humans. If you want to hang on to that I’ll try and identify it later.’

Prabir dropped it in his backpack. ‘You think plants could be affected, too?’

‘It probably just blew in on the wind from somewhere.’ Suddenly she grabbed his shoulder. ‘Look!’

Ten metres away, a jet-black cockatoo exactly like the one they’d seen in Ambon sat perched on a branch, watching them.

Prabir said, ‘That’s one for the migration theory.’

Grant was conceding nothing. ‘If four different species on Bandanaira can converge to the point of being indistinguishable, I don’t see why the same thing can’t happen independently here and on Ambon.’

Prabir scrutinised the bird uneasily. The teeth embedded in the bill not only meshed with uncanny precision, they were limited to the sides of the jaw, where the upper and lower halves met; the great curved hook in the centre had none. Even if they offered no particular advantage, they certainly weren’t present at any point where they’d be utterly useless, for want of a matching surface to cut or grind against. But the specialised bill shape that suited the diet of an ordinary black cockatoo would have evolved long after its ancestors had given up on the whole idea of teeth, so how had the ancient reptilian genes supposedly responsible for their reappearance come to be switched on and off in exactly the right places? Why should two sets of genes that had never been expressed in the same animal before turn out to interact so harmoniously?

Grant took aim with the tranquilliser gun. The dart hit its target and stuck, but didn’t take effect as rapidly as it had with the much lighter pigeons. The cockatoo rose from its perch with an outraged squawk, featherless red cheeks flushing blue, and swooped straight towards them, almost reaching them before it fell.

Prabir pushed forward to try to find it in the undergrowth while the arc of its descent was still fresh in his mind. Grant joined him. They combed through the shrubs together for five minutes without success; the bird must have been heavy enough to sink through the vegetation right to the ground.

Grant swore suddenly.

Prabir looked up. ‘What?’

She was forcing branches and leaves aside with both arms; maybe she was annoyed because she couldn’t pick up what she’d found. She said, ‘Come and have a look at this.’

Prabir complied. Tiny black ants were swarming over the motionless creature, which was more pink now than black. It was already half eaten.

‘Did that look like carrion to you when it hit the ground?’

‘Hardly.’ Prabir reached down gingerly; he didn’t particularly want to fight the ants for their meal, but it would be too much hard work to give up and go looking for another specimen every time something like this happened.

‘Be careful,’ Grant advised him redundantly.

He grabbed one bedraggled wing between thumb and forefinger and tried shaking the carcass clean. Ants swarmed on to his hand immediately; he dropped the dead bird and started swatting them. He crushed most of them in a matter of seconds, but the survivors continued doing something extremely painful—stinging or biting, they were too small for him to tell.

Grant fished out the repellent and sprayed his hand; they’d never thought before to be so thorough. The solvent itself smarted; his skin was broken in a hundred places.

‘Are you OK?’

‘Yeah, yeah.’ His hand was throbbing, but if he’d been stung he didn’t seem to be suffering any systemic reaction.

Grant sprayed her own right hand, and the carcass, then broke a branch off a shrub and used it as a hook. There wasn’t much flesh left on the bird, but it would be more than enough for DNA analysis.

‘At least they weren’t army ants,’ she joked. ‘We’d be lucky to have salvaged anything.’

Prabir eyed the ground nervously. ‘No, but I didn’t think we were in Guatemala.’ His old implant might have given him a rose-coloured view of Teranesia’s insects, but he was sure there’d been nothing as aggressive as this.

He said, ‘If this whole thing is a response to genetic damage, wouldn’t it have shown up in some experiment by now? They’ve been irradiating fruit flies for a hundred years, at every conceivable dosage.’

Grant was way ahead of him. ‘Maybe it has shown up. But one or two individual recovered traits wouldn’t necessarily stand out clearly from genuinely fortuitous mutations. It’s not as if the entire organism would regress to an archaic form that any competent palaeo-entomologist would recognise instantly. I think what’s happening with the displaced organs in some of the mutants is that part of the embryology has been modified out of step with the rest; the result isn’t harmful, because there’s so much conserved across the gap, but it leads to some detailed anatomy that’s neither modern norarchaic.’

‘Right.’ Prabir still couldn’t see how the cockatoo’s teeth had come to be placed so efficiently, but he didn’t know enough about the subject to argue the point with any confidence. ‘But when you look at the original DNA of the pigeons that used to live on Bandanaira, can you see where the recovered traits have come from? Can you pin down the sequences that have been cleaned up and switched on in the birds we saw?’

Grant shook her head. ‘But I don’t expect to be able to do that until I understand how the repair process works. The original sequence might be cut out and spliced into a new location, and even hunting through the whole genome for partial matches wouldn’t necessarily find it.’

Prabir thought this over. ‘So what you really need to do is catch it in the act? Instead of just seeing the “before” and “after” genomes, if we could find an animal where the process was still going on—’

‘Ideally, yes,’ Grant agreed. ‘Though I don’t know how we’d recognise it. I don’t know what we’d look for.’

Nor did he. But it might still be happening most often, and most visibly, on the island where it had happened first.

Any lingering fear of retribution from Grant was absurd; they were friends now, weren’t they? And however annoyed she might be that he’d lied to her, she was hardly going to abandon him here.

But Madhusree had promised to say nothing. How would she feel if he broke the silence first, without consulting her? And if Grant scooped the expedition with his help, the discovery wouldn’t become public knowledge, it would be the property of her sponsor.