Its ceiling and its walls were far enough away to be invisible. Weird wails and lowing sounded distantly from all sides. As their eyes adjusted, cages walled with dark wood or iron or reinforced glass loomed at them irregularly in the enormous hall. Some were huge, the size of rooms: others were no larger than a book. All were raised like cabinets in a museum, with charts and books of information slotted before them. White-clad scientists moved through the maze between the blocks of glass like spirits in a ruin, taking notes, observing, pacifying and tormenting the cages’ inhabitants.

Captive things sniffed and grunted and sang and shifted unreally in their dim prisons.

The cactus walked briskly off into the distance and disappeared. The woman carrying the grubs made her way carefully through the room.

Things lunged at her as she walked past and she shuddered with the glass. Something swirled oleaginously through a huge vat of liquid mud: she saw toothy tentacles slapping at her and scouring the tank. She was bathed in hypnotic organic lights. She passed a small cage smothered in black cloth, with warning signs plastered ostentatiously on all sides and instructions on how to deal with the contents. Her colleagues drifted up to her and away again with clipboards and children’s coloured bricks and slabs of putrefying meat.

Ahead, temporary black wooden walls twenty feet high had been thrown up, surrounding a floor-space forty feet square. Even a corrugated iron ceiling had been hammered over the top. At the padlocked entrance to the room-within-a-room stood a white-suited guard, his head braced to take the weight of a bizarre helmet. He carried a flintlock rifle and a back-slung scimitar. At his feet were several more helmets like his.

She nodded to the guard and indicated her desire to enter. He looked at the identification around her neck.

“You know what to do, then?” he asked quietly.

She nodded and put the box carefully on the floor for a moment, after testing that the string was still tight. Then she picked up one of the helmets by the guard’s feet and slipped the unwieldy thing over her head.

It was a cage of brass pipes and screws that slotted around her skull, with one small mirror suspended a foot and a half in front of each of her eyes. She adjusted the chinstrap to keep the heavy contraption steady, then turned her back on the guard and fiddled with the mirrors. She angled them on their swivelling joints until she could see him clearly directly behind her. She switched focus from eye to eye, testing the visibility.

She nodded.

“All right, I’m ready,” she said, and picked up the box, untying it as she did so. She stared intently into the mirrors while the guard unlocked the door behind her. When he opened it he averted his eyes from the interior.

The scientist used her mirrors to walk backwards quickly into the dark room.