Beneath the shell were two huge, iridescent green eyes. They could not blink, it seemed, nor change shape in any way, and thus gave no indication of the creature’s displeasure at being handled this way. The tentacles were long and whip-like, and they sought out Gideon’s hand and encircled his wrist. With several of its limbs occupied this way, the underside of the animal was revealed, pale and dotted with suckers, a small beak opening and closing like a feeding parrot. Those eyes shone out from within the nest of exploring arms, and I felt as though they were staring at me.

Gideon swept the tentacles off himself until they hung vertically below the shell. Then he took a firm hold of the animal around the point where its large eyes were, and pulled on it. It came free from the shell. Now I could see the head, a little narrower than I had imagined an octopus’s head to be. He tossed the creature back into the bucket and it immediately inked, squirting jet-black droplets out of the water and onto a nearby pile of books. We watched it dart around the bucket before compressing itself into the angle where the bucket’s sides met its base.

‘Hmm,’ he muttered. ‘That’s the first observation, then. Animal survives separation from the shell.’

He held the shell aloft. It was unblemished, white as quartz and slightly translucent, so that the yellowy light of the lamp passed through it and showed the shadows of his fingers beneath. Along its radial spine the tiny lumps were raised into little horns, each slightly larger than its predecessor.

‘It drifted by the boat yesterday and I scooped it with a net. Lovely specimen, is it not?’

I agreed that it was. He used a small cloth to pat it gently dry, then placed it on a bookshelf behind the desk. Now he sat at an odd-looking occasional table beside the desk that I hadn’t noticed before—another large item in the room that had appeared from nowhere.

It was not just a table, I realised, but a mechanical device of some kind, its function a mystery to me. The doctor bent and tended to it: adjusting a structure that resembled the base of a treadle sewing table, but with a leather bellows attached to one side. The nose of the bellows, pointing upwards, was connected to a tube that ran up and followed a metal arm to a box located at the user’s eye height.

The device fascinated me because I knew instinctively that it was a product of the doctor’s mind. He had not ordered it from a catalogue, nor commissioned an engineer to make it for him. It came from within him, a mechanical expression of the intricacy of his thinking. Having first dismissed him as a carnival hustler, I was now becoming intrigued by his abilities.