‘Watertight holds. A feature of these great vessels. See? Hole one of them and it will flood but the ship won’t sink. The shipwrights of the west have got a lot to learn.’ But then his eyes clouded, a look of confusion returned to his gaunt face, and he retreated inside himself.

They had to clamber down a short stair, Pyxeas managed with difficulty, to the small cabin that had been allotted them. There were two narrow bunks, one table, a few shelves with rails to stop their possessions falling off when the ship rolled, and a tiny glassless window through which a stiff breeze pushed, bearing a scent of smoke from the fires on land. Bayan and the other crew crowded around, their hands held out. Avatak had a pouch of coins at his waist; he doled out one to each man. He had spread his wealth around a number of pouches and satchels and pockets, including a few of Uzzia’s gems, most of which were still sewn into the quilted coat, which he wore. He hoped that these layers of deception would distract thieving fingers enough to enable them to reach Carthage with some of their wealth intact.

Now the turbaned captain pushed into the cabin, carrying a slate. His nose was strong, his face masked by a grey-flecked beard, but his large, dark eyes were oddly gentle as he inspected Pyxeas. ‘You are the scholar? And his man.’ His Northlander was passable.

Pyxeas stood and drew himself to his full height. ‘I am he, Pyxeas,’ he said in rich Northlander, and repeated the words in Persian. ‘The boy is called Avatak.’

The captain made tick marks on his slate. ‘Good. You may call me al-Quds. It is not my name, which nobody in Cathay can pronounce, but it’s the name of the holy city where I was born, and it’ll do.’

‘I will need quiet,’ Pyxeas said sternly. ‘I have work to do – vital work. I must not be disturbed. You cannot comprehend the importance.’

‘Can I not?’

Pyxeas glanced around at the cabin, the tiny table. ‘I suppose this must suffice.’ He sat uncertainly on one of the bunks.

The Arab raised his eyebrows at Avatak.

Avatak shrugged. ‘He’s a scholar.’

‘Well, for the next months, he’s to be a scholar and a sailor.’ He eyed Avatak. ‘What are you, a Mongol? Not a Northlander.’

‘Not a Mongol. From very far west.’