He gave the swarmer a squeeze. If he’d been holding a rat, the pressure of those sausage-thick fingers would have shattered its bones and crushed it into a gooey paste, but the swarmer was roughly the consistency of a hard rubber ball and it simply continued to stare at him. Mr Black put his head on one side, then smiled.

‘Tough little bastard, ain’t you?’ He turned towards the furnace. ‘Let’s see how you like a little fire.’

‘Get him,’ Alice whispered.

The other five swarmers rushed forward, charging beak-first like a wedge of medieval lancers. The needle-sharp points struck Mr Black around the ankles, piercing the thick leather of his boots. At the same time, the swarmer he was holding twisted in his grasp and sank its beak into his hand, in between his fingers and thumb.

The huge man roared like an animal, so loud that Alice retreated from the swarmer’s senses and clapped her hands over her ears. He threw the swarmer he was holding against the wall, hard, and it ricocheted off like a tennis ball and rolled across the floor. The others ran for it, just ahead of his reaching hands, and scurried back towards the door.

As she’d hoped, Mr Black followed. Alice kept the swarmers in a group until Mr Black cleared the doorway. He charged, head lowered like an angry bull, and they scattered. He aimed a kick at one that moved a bit too slowly, and sent it ricocheting off the wall to land among the crates with a crash of splintered wood. Mr Black roared again and went after the others, who scurried and dodged to stay ahead of him.

Go, Alice willed Isaac, and she was gratified to catch a glimpse of him darting towards the furnace room. Mr Black was in a rage, kicking over boxes and smashing neatly piled stores to get at the swarmers. Alice began to smile. It was almost fun, trying to keep ahead of him – the swarmers could get under and around things he would trip over, and even when he caught up, his swats and kicks did the durable little creatures no real damage.

It serves him right, she thought as he stumbled over a crate and crashed headlong into a sack of potatoes.

Mr Black stopped thrashing about. He raised his head and gave a low, animal growl. Then he sniffed the air, like a hound catching a scent.

‘Very clever,’ he rumbled. ‘Oh, very clever.’ He straightened up, extricating his feet from the ruin of the crate. ‘You thought you’d have some fun with poor old Mr Black?’

There was a tremendous crash and clatter as Mr Black hurled a box of crockery out of the way and closed the distance with Alice in two enormous strides.