He was thinking this way on a hot Thursday night, when they weren’t more than a hundred miles from Cayos Miskito, off the coast of Nicaragua, and less than 350 miles from Aspinwall, on the isthmus of Panama. The ship’s sails were up, because there was a light easterly wind, and they were rippling in the darkness, while beneath the decks the steam-powered engines were pumping and pounding as they turned the paddles around. Collis lay awake for a half-hour, and then he gradually eased himself off his bunk, dressed in nothing but his sweaty striped nightshirt, and climbed to the floor.

The Latvian was fast asleep, breathing out slivovitz fumes through his tousled beard. Collis stepped carefully over his parcels and packages and unbolted the cabin door. In the dining-saloon outside, the lamps had been turned low, so that they glowed dim and orange, and the passengers lay wrapped up in their blankets in different exaggerated postures of sleep, mouths open, hair tangled, necks at awkward angles. Collis passed by them all and padded down the saloon to the door which led out on to the deck. Someone snorted and turned over.

It was dark and windy outside. There was no moon yet. Collis’s nightshirt flapped around his legs as he closed the saloon door behind him and stepped out on to the deck. The ship’s paddles churned up an odd luminescence in the water, dark blue and shimmering, and there was a sharp smell of smoke on the breeze.

He made his way forward, along the promenade deck, until he reached the rail where the flag of the Atlantic Mail Line rumbled and snapped. He stood there for a while, breathing in the warm wind, and then he made his way back to the door that led to the women’s cabins. There was nobody looking, and on the deck above him, in his wheelhouse, the helmsman was crouched over his lamp writing a letter; so Collis quickly opened the door and stepped into the shadowy passageway inside.

He paused for a moment. The passageway smelled of cologne and urine. He listened to hear if anyone was awake, and then he tiptoed along to the third door, and knocked.

There was no answer. He knocked again, harder this time, holding his breath. He heard a rustling of sheets, and then a whispered voice say, ‘Who is it?’

‘Hannah? It’s me, Collis.’

‘Collis? What do you want? What time is it?’

‘I don’t know, maybe two or three o’clock. I’m not wearing my watch.’

‘What’s the matter? Can’t you sleep?’

‘I was thinking of you, Hannah.’

‘What do you mean?’

He paused. He wanted to be sure that he phrased this in just the right way. He said, ‘I need to talk to you. It’s important. I feel that something important is slipping away from us.’

‘Collis, whatever it is, we could just as easily discuss it in the morning. You shouldn’t be here. These are the ladies’ quarters.’