‘I’m filthy,’ Ashes said. ‘And I think one of them may have nipped off a bit of my tail.’

Alice closed her eyes and blew out a long breath. All her limbs felt shaky, but she managed to climb to her feet and look around.

The results of her survey were disappointing. She’d been hoping for a barrier she could put between herself and the Swarm, and she’d found one, but the space on this side was barely larger than a closet and there were no other exits. In one corner was the source of the sound of rushing water: a fat pipe on the ceiling gushed a continuous torrent into a brick basin, which drained away through a cast-iron grating. Alice gave this last a long look, but even if she’d been able to remove the rusty grate, the hole was too narrow for her to squeeze into.

A hollow bong filled the room for a moment, making her jump. It was repeated a moment later, then twice more, and when she put a hand on the door she could feel it reverberating from the impacts. She pictured the corridor outside filling with swarmers, hurling themselves into the air like living missiles, hammering at the portal . . .

She gave it a tug, and it seemed secure. The bangs continued, but Alice breathed a little easier.

‘I hate to say this,’ Ashes commented, ‘but our situation has not materially improved.’

Alice gave the door a bang. ‘This seems like an improvement to me.’

‘Only if you intend to remain here until you starve to death.’ The cat, in the corner furthest from the falling torrent of water, bent and began to lick his fur. ‘And while I might be able to survive for some time by eating your corpse, in the end the same applies to me.’

Alice closed her eyes and gave a hysterical giggle. ‘Who says you get to eat me, and not the other way round?’

‘It’s only logical, given our relative sizes,’ Ashes said, still grooming. ‘I’d be barely a mouthful.’

Alice took a deep breath for the first time in what felt like hours.

‘Nobody is eating anybody,’ she said. ‘We’ll just have to think of something.’

A short while later, after a detailed examination of the room, she had the beginnings of a plan.

A brief inspection of the walls had turned up a brick that had cracked in half, and from the loose section Alice had broken off a vaguely wedge-shaped fragment. With this she attacked the mortar around some of the bricks beside the doorway, at about head-height. Her tool was crude, but the mortar was so old, wet and rotten that some of the bricks were loose to begin with. After a little bit of work, she managed to lever a couple out of their sockets, and went to work on another pair a little further down.