From the air, James saw fire erupt from the ground, a line of searing fountains. Monks and novices squirmed out of hatches like moles emerging from their holes, and ran off. James understood immediately. The fire was breaking out of the ground through the air vents of the underground manufactory. The explosions must have come from within the compound. It was the store of gunpowder, it could only be that. Some accidental spark had ignited it - or perhaps, he thought suddenly, it had been deliberate.

James had to concentrate on his own flight. His mechanical bird was dipping towards the ground. He had only a few heartbeats left in which he could control his descent. He scanned the ground anxiously, looking for a clear space to land.

But a fresh set of explosions broke out over the location of the main manufactory, distracting him, and James saw bones hurled into the sky. The gunpowder must have broken open a plague pit. It was an extraordinary, unnatural sight to see those bones go flying up into the air and then fall back, a grotesque parody of the Day of Judgement.

XIX

XIX

Harry, with Abdul and Geoffrey, had been watching the display from a distance, with appalled fascination. The wooden bird in the sky especially was an awful, unnatural sight.

But when the fires began to erupt from the ground they all knew something had gone badly wrong. Abandoning all attempts to conceal themselves, they ran towards the party coming from the viewing pavilion.

They met the others not far from the entrance to the manufactory. The explosions had stopped now, but smoke still poured from the ground. No more monks clambered out of the hatches, and Harry wondered how many had died that day.

Diego Ferron was unmistakable, a tall, pale cleric. He was holding a woman by her hair, a wretched, skinny girl in a grubby white gown. Beside Ferron and his captive was Grace Bigod. She was a hard woman of nearly fifty, her face smeared with soot and twisted in fury. It was the first time Harry had met this remote cousin.

Ferron seemed surprised to see Abdul with two strangers, but his rage overwhelmed him. In accented Latin he cried, ‘Ruined! Destroyed! Centuries of work lost!’

‘Not lost,’ said Grace, her voice trembling, ‘Just delayed. We have lost our engines, but those in the field survive, and we have the designs—’

‘Lost because of this Christian witch!’ He twisted the girl’s hair and threw her to the ground.

She lifted her head. She looked straight at Harry. Her hair fell away from a bruised face.

‘Agnes!’ He could not have been more shocked if his sister had been raised from the dead. ‘But you are in your cell in York.’

‘Evidently not,’ she said. Her voice was a scratch, and she coughed, her lungs full of smoke.

Grace looked at Harry and Geoffrey. ‘Who are you?’