II

Knox waded out to the Yvette, then spent a few minutes studying the chart of the Eden reefs pinned to the cork-board. Nothing he’d learned so far had given much support to his hunch that Adam and Emilia’s disappearance was connected to their upcoming salvage; but nothing had disproved it either. And, rather than simply search the sea at random, he might as well look for the wreck-site too, if only to ease his conscience about Miles.

Emilia had been secretive about its precise location, but she’d let slip a few clues all the same. He knew, for example, that it lay a little over thirty metres deep. That cut out all of Eden’s lagoon, which was twenty-five metres at its deepest, as well as everything beyond the pelagic boundary. She’d also told him that she and her father had found it during a routine coral check. This involved visiting particular sections of the reef month after month, year after year, to examine them for bleaching and other symptoms of ill health. While their secrecy about the wreck would surely have precluded them from marking its location, this chart appeared several years old, so it seemed probable that the coral they’d gone to check that day would have been marked upon it. But which mark? There were three or four hundred of them on the chart, and he didn’t even know which ones represented corals.

He unpinned the chart, looked at its reverse for a key.Nothing. He turned to the map-stand instead, pulled out and checked the other charts in turn, again without success. He did, however, find another old chart rolled up at the bottom. He hadn’t noticed it before because it was shorter than the others, and shorter than the top of the stand. It was a vaguely familiar reproduction of an ancient world map, but of very poor quality, blurred black-and-white printouts cut into a collage and glued to a backing sheet. He took it out into the sunshine for a better look, which was when he realised why he was having trouble recognising it. He was holding it upside down.

It was a commonplace, these days, to blame Western arrogance for the orientation of maps with north on top and Europe at the heart. But Knox had little truck with that view. Apart from anything else, it would be perverse to expect a map-maker to place their home anywhere but at the centre. As for putting north on top, that was less to do with arrogance than with rivers. The ancient Egyptians, for example, had based their lives around the Nile. The Nile had flowed from south to north; water flows downhill; it had followed that the south had been Upper Egypt, and the north Lower. Claudius Ptolemy, on whose great work Geography modern maps are indirectly based, had lived in Alexandria, and so he might easily have adopted the Egyptian style. But he was also Greek, and the Greeks put north on top. For many centuries after the schism that split Rome from Constantinople, however, Ptolemy fell into obscurity in Europe. And when medieval Christians started making maps of their own, they put east at the top, not north, for they had seen the world as a cosmic metaphor for Christ, in which the rising sun represented his haloed head. The Arabs, meanwhile, put south at the top of their maps; and, because they were the great seafarers of the age, the many cartographers who borrowed from them did likewise. One of these was a Venetian monk called Fra Mauro, and it was a copy of his 1459 map that Knox was holding now.

The map wasn’t just notable for being upside down, however. Fra Mauro had written notes to accompany his creation, even crediting his sources, though often leaving them unnamed. According to one of these, a huge ship had arrived at the Cape of Good Hope from the east in around 1420, then had sailed off westwards for two thousand miles or so before giving up and coming back. It was hard to be sure from the terse description, but it certainly could have been a treasure ship, especially as the dates tallied so perfectly with Zheng He’s sixth voyage. If so, it was the only recorded sighting of a treasure ship that far south, that far east. And it had been on its own.

Knox’s working assumption had been that, if Adam and Emilia had really found a Chinese ship on these reefs, then it had been a second ship from the same fleet as the one Cheung had found further north. But the presence of the Fra Mauro map suggested that the Kirkpatricks, at least,had considered a simpler explanation: that there was only one ship, the very same one that had been seen twice at the Cape of Good Hope.

Ricky Cheung had been dismissive of Fra Mauro and his source. A single treasure ship hadn’t fitted his preferred narrative of a vast Chinese fleet making it to the New World, mapping it and establishing settlements before sailing back home. Besides, Fra Mauro’s source had been emphatic that the ship’s crew had found nothing at all on their two thousand mile voyage west. Nothing but sea. Yet Knox had always wondered about that.

After all, they would have said that, wouldn’t they?