‘Dipping room,’ she gasped, and then pushed past him.

‘And where’s that?’

‘Down the corridor, on yer right. Lemme go, mister.’ She tore her arm out of his grip and ran.

The long, low room was almost empty now, but he could hear the roar of machines from next door and he ran in to find the workers still labouring in spite of the smoke, choking as they tied the matchboxes into parcels. Now he knew that the spell was bound up in the machines it was easier. He didn’t waste time begging or trying to shake them out of their indifference, he just went straight for the belt with his knife. There was the same grinding, shrieking roar, like the dying screams of the machine, and then it snapped and the workers were dazed and staggering like new-woken drunks, the room ringing with his shouts as he harried them towards the stairs.

The smell of smoke was very strong now and he could hear the crackle of flames, but above it was another smell, something acrid that tore at his throat. And still he had not found Minna – or Rosa. Had she come back here? Back to Sebastian’s waiting arms?

He tried to remember her parting words as he ran up the corridor, the muffler pulled high across his face to try to shut out the bitter, choking fumes, but he could not. All he could remember was the horror in her eyes as he raised that hammer and she ran.

Down the corridor. On your right.

There was a door. It was marked ‘no entry’. There was smoke and the red glow of flames coming from the crack beneath. Luke touched it with his hand and it was hot. He pulled off his muffler, wound it around his hand, and grabbed for the handle.

Inside, Hell met his eyes.

Wherever the fire had started, it was close to this room, and the flames were eating at the dividing wall and flickering up through the floorboards, attacking the joists beneath. But – impossibly – the workers still toiled, stirring at the great vats of chemicals that bubbled in the centre of the room, a white mist rising off the surface.

Luke stepped forward, ready to slash at the dipping racks, up-end tables, douse the stoves. He would free this last group and get out.

Then he stopped.

Standing between the vats was a man, his figure just a black outline against the smoke – but Luke did not need to see his face to recognize that tall silhouette. It was Sebastian Knyvet.

Luke swallowed. He thought about running – but what if Minna were here, in this last room? He couldn’t fight his way through all this and then run without even freeing her. But if Knyvet saw him . . .

It seemed like an eternity as they both stood, frozen as the flames flickered around them. Could Knyvet see him? He couldn’t tell. His shape was wreathed in smoke and flame, his face hidden.

And then Sebastian moved. He grabbed the lip of the cauldron closest to him, seeming not even to notice the scalding metal on his bare hand, and heaved.

Toxic, boiling chemicals flooded across the floor, hissing and spitting, throwing up an acrid white smoke that made Luke gasp and retch and the workers fall back. A girl almost staggered into his arms and Luke caught her reflexively.

‘Luke?’ she gasped.

‘Minna!’

It couldn’t be the phossy jaw – not yet, surely? But it looked very like it. Her face was swollen and livid, and the tooth that had given her so much trouble was missing; where it should have been there was a bloody gap for the phosphorus to enter, rotting the bone from within.

‘Get out,’ he said urgently. Minna shook her head, looking back at the dipping racks with an expression almost like longing, and Luke wanted to slap her.

‘Get out, Minna! There’s no more dipping – this place is burning down – can’t you see?’

The flames were licking at the dipping racks and the drying frames now, the dipped matches bursting into flames as the heat began to reach them. One of the racks collapsed in a shower of sparks and miniature explosions.

‘Get out!’ He took her shoulders and shook her, trying to reach her through the thick cloud of spell and stupor.

She opened her mouth – and then shut it again and nodded once. Then she stumbled from the room.

Luke watched her go and then turned back to try to persuade the others. It was too late for some; there were bodies on the floor overcome by the smoke. But others were staggering out into the corridor, making for the stairs further from the inferno.

Another drying frame went up with a roar. The fire’s heat was becoming intolerable. It had taken hold now – there was no hope for the factory. He had to get out, or burn with it.

Luke turned to go. As he did, he cast one last glance at Knyvet, wondering if the man was planning to burn.

He had turned. He was standing in the centre of the room, wreathed in flame and smoke. His head was bare and his pale hair was bright in the dancing flames. And there was something in his hand. Something that made Luke stop dead in his tracks.

An ebony shaft. A twist of silver. A shape that had dwelled in his nightmares for so long: a coiled snake.

The Black Witch.

No. He shook his head, the smoke swirling in his skull, making him numb and stupid. It was impossible. Sebastian was far too young to be the witch he’d seen.

But that cane – it was unmistakeable.

Then Knyvet spoke.

‘So you came back for her.’

Luke felt frozen. His face was burning, but his hands were cold as ice. As cold as Knyvet’s blue, blue eyes.

‘You. Where did you get that cane?’ he managed.

‘You’ve come all this way to discuss gentlemen’s accessories?’ Knyvet laughed. His smile was horrible to see; he had been slashed all across one side of his face, so that the bone gleamed through the flesh, pink and white in the burnt skin.

‘The cane!’ Luke snarled.

‘Much as I’d like to discuss fashion with you,’ Knyvet gave that horrible death’s-head smile again, ‘I fear I must leave.’

Luke looked behind them, at the stairs. The exit was gone, the stairwell filled with flames – a great hole where the landing should have been. Something shifted beneath their feet and a joist gave way with a groaning crash. Luke clutched at a table, but Knyvet turned towards the window, pointed his cane and shouted a spell in some kind of foreign tongue, words Luke didn’t recognize. Glass and bricks flew outwards like an explosion, leaving a jagged hole in the wall, large enough to jump from, if you were a fool, or suicidal. The night air whistled in, fanning the flames higher.

‘Goodbye,’ Sebastian drawled. ‘How lovely that you and Rosa can be together at the end. Such devotion.’

Luke went cold.

‘Oh.’ Sebastian began to laugh. ‘You didn’t know? She’s having a little tea party upstairs – tied up, as you might say. Unfortunately our delightful afternoon was brought to a close by her announcement that she intended to expose my family’s practices and bankrupt the factory. Not the act of a devoted fiancée, wouldn’t you say?’

‘What?’ Luke tried to clear his head. He held on to the table, his fingers numb. The smoke was choking him, making him almost too dizzy to stand. His eyes were streaming. ‘She threatened you?’

‘Yes. I don’t take kindly to blackmail – and it’s never a good idea to give an ultimatum. You might find the person prefers a third option, one you didn’t offer. You’re welcome to her – what’s left of her. I doubt it’ll be much.’

And then he ran towards the jagged hole and leapt.

For a minute Luke held his breath, waiting for the smash on the cobbles below, the screams from the workers. It never came and he stumbled to the gap, feeling the cool wind on his face.

Knyvet was hovering in mid-air, high above the workers beneath. There was a smile on his face. Then he turned and skimmed above the rooftops, far out of sight.

Luke looked down, his heart in his mouth. It was a long drop – perhaps thirty feet – on to cobbles. But it was better than burning. And he had every reason to live. He thought of the cane in Knyvet’s hand, the cane that held the answers to the mystery of his parents’ death. Knyvet knew – even if he had not carried out their execution, he must know who had killed them, and why.

Luke could not take him on alone, but with the Malleus at his back . . . He looked at the sky. Far above the sluggish Thames, the moon was full. It was the last night of his task. If Rosa died tonight, he could live; live to fight side by side with William and John and the rest of the Malleus, live to kill Sebastian, live to avenge his father and mother.

He held on to the jagged bricks of the opening. Jump, you coward.

But . . . Rosa.

Jump.

Rosa.

Coward.

The words pounded inside him, in time with his pounding heart, like a hammer.

Rosa!

He did not jump.

He turned and ran back into the factory.

It was hot in the little office. Unbearably hot. And the room had begun to fill with smoke.

At first Rosa had screamed, or tried to, her throat growing raw and her lips bruised as she worked her mouth around the choking gag, until at last it was between her teeth like a bit and she could pant and shout, albeit muffled.

But no one came. Between cries she listened. She could make out the sound of smashing machinery and the far-off crackle of fire. At one point she thought she heard shouts and running footsteps, and she screamed again, louder, but whoever it was either couldn’t hear her above the noise of the dying factory, or else didn’t care enough to stop.

How could she ever have promised to marry Sebastian?