She pushed the latch and gave the door a tug, pulling it inwards a fraction of an inch. Almost immediately the swarmers on the other side pushed forward, shoving the portal open and spilling into the room with triumphant quirks while a flood of water flowed around their legs and into the corridor. Alice jumped for her handholds on the wall, felt her fingers slip on the wet brick for a heart-stopping moment, and managed to hang on by digging her nails into the mortar. She risked a look down – the door was half open now, and more and more of the little black creatures came into the room, carpeting the floor until it was a seething, quirking mass of swarmers. The ones closest to her started to jump for her exposed feet, but they couldn’t quite get the height they needed to reach her, and their beaks rasped against the brickwork.

‘I don’t mean to be a bother,’ Ashes said, his claws now gripping tight enough to draw beads of blood, ‘but I fail to see how this has helped.’

‘Hang on,’ Alice said.

‘I wouldn’t dream of doing anything else.’

The water pouring out of the basin was now flowing into the corridor in a steady stream. The edge of the door was only a foot away, but it still required all of Alice’s courage to reach out to it, endangering her precarious position by shifting her weight. A bit of mortar crunched under one foot, and she stopped breathing, but she didn’t slip free. Her fingertips found the door and pushed. Slowly at first, hinges protesting, the door started to close. The swarmers in its path quirked indignantly and pressed into the room, climbing atop the living carpet of their fellows. Alice pushed harder, and the door swung shut with a resounding boom and a click from the latch.

The iron door wasn’t quite watertight, but it was the next best thing. The flood that had been escaping into the corridor now had nowhere to go, and within moments Alice could see the water level in the little room rising. Inch by inch, the cold stream spilled over the lip of the basin and started to climb up the walls.

Ashes eyed it balefully. ‘Do you think they float?’

‘No,’ Alice said. ‘I picked one up earlier, and they’re much too dense.’

The rising water covered the swarmers’ legs now. The living carpet writhed, trying to escape, and more and more of them threw themselves at the brickwork by her feet. A few even managed to find scrabbling holds, digging their beaks into the mortar, but they couldn’t hang on for more than a few seconds before falling back into the mass.