‘I shall return shortly,’ he muttered now. He picked up the tray and its eviscerated bird, and followed my father downstairs.

I was left on deck by myself, just the night and the two Connollys playing cards nearer the bow. I knew the hands, the tricks: Declan was letting his brother win. I went to the rail and looked out at the night and saw the Moonbird’s wake glowing bright green in the darkness. The glow flared where the water was disturbed up close against the edge of the bow, then faded as the little bow-wave rolled away from the timbers and out into the night.

The doctor appeared at the rail beside me, smoking his pipe.

‘It’s enchanting,’ I said.

‘Not Ehrenberg…’ He tapped an irritated index finger on the rail, as though he was trying to dislodge something from his memory. ‘Boyle! Robert Boyle has written on it. Luminescence… animalcules, he called them.’

‘Boyle…the one who invented that pump you showed me?’

‘Yes! The very same.’

I looked at his face, the bent and imperfect riddle that it was, and I saw the glow reflected in it. I wondered to myself why it wasn’t enough that the glow was there and that it was beautiful.

‘I have one more thing to show you,’ he said now. ‘Are you tired? Would you humour me a little longer?’

I shrugged and told him I could spare him a minute or two.

‘I would appreciate it, you know. Too much of the work is solitary. Come, then.’ He tapped out his pipe on the rail and indicated that we should go below. I followed him, past my father’s curtained bunk, the doctor making an exaggerated shushing gesture with his finger on his lips. Out of the gloom and into his cabin, the curious assemblage of boxes and instruments, books and jars and skulls and feathers, a room inhaling more and more objects: not just the specimens, which were undoubtedly growing in number, but large items I was sure I’d never previously seen.

‘Look!’ He was peering into a tin bucket that was set on the floor beside the desk. He scooped his fingers through the water and brought up a most exceptional creature: an octopus of some kind, slightly bigger than his hand and wearing a white spiral shell where one might have expected to see its head. The shell was rippled and serrated in many different directions: there were no smooth surfaces but hundreds of small bumps that formed complex patterns, all of them leading back into spirals that complemented the winding shape of the shell itself.