‘Goodnight, Mrs Greenwood.’ Sebastian turned and took his top hat from James, who was waiting in the doorway with his coat and cane. He raised his hat to Mama, nodded to Alexis, and left.

Mama watched from the window as he made his way down the dark street, the thick yellow fog swirling in his wake, until it closed around him and it was as if he’d never been there at all. Then she turned to Rosa and her face was hard.

‘Tomorrow you will ask Clemency to send for her dressmaker, and we will fit you for a new habit.’

In the middle of the night Rosa woke. It was very late; she wasn’t sure how late, but gone midnight. But a light showed faint and flickering beneath her bedroom door, from a corridor that should have been dark. Impossible that the servants would be up so late. And it wasn’t Alexis; she could hear his snores coming from the other end of the house.

Gathering her nightgown, she swung her legs out of bed and stood, her heart beating in her throat. It was stupid to be scared. If it was burglars, she had more weapons than they did.

Rosa whispered a spell beneath her breath, a charm to give herself courage. And then she opened her bedroom door.

The corridor was dark, but she could see where the light was coming from: the study door was ajar and the glow of a candle cast a long golden streak across the threadbare hallway runner. Rosa padded closer, her bare feet silent on the soft rug. As she drew near she took a deep breath and held it, tiptoeing the last few feet.

It was the book she saw first, open on the study table. It was bound in thick fading leather with a small brass lock and gold embossed letters that read The Holy Roman Catholic Bible. But it was not a Bible. That cover was only for the servants. Inside, beneath the lock, was something very different. Not the family Bible, but the family Grimoire, handed down from mother to daughter, with spells added by every generation, notes on poultices, scribbled additions in the margins: If rue cannot be found, then the dryed herb will serve very well, only let the mix be steep’d another night . . .

It was the most precious possession in the whole house – and the most private. And someone was reading it. In secret.

Rosa flung open the door with a furious bang. Then her mouth fell open.

Her mother looked up, her face white, her eyes wide and full of alarm. She was in her nightgown, her hair in a thick plait down her back.

‘Wh— Rosa!’ She let out a shaking, exasperated breath. ‘Good Lord, child. What are you doing sneaking around in the middle of the night?’

‘I could ask the same! What are you doing with the Grimoire?’

‘It is none of your business!’ Mama snapped. She slammed the book shut, flipped the brass lock. But not before Rosa had caught sight of the heading: A Silver-Tonguéd Charme – to Persuade the Reluctant to yr Course.

‘Mama . . .’ They stared at each other in the candlelight. Her mother’s handsome face became hard, stubborn. ‘Mama, tell me you’re not meddling with Sebastian. It would be suicide to do this to an Ealdwitan. If he found out . . .’

‘There is nothing to find out.’

‘Then why—’

‘Hold your tongue!’ her mother hissed furiously, and she pointed at Rosa. Magic crackled from her fingertip and Rosa’s mouth snapped shut like a trap, so hard she bit her tongue and tasted blood. She breathed through her nose for a long moment, tempted almost beyond endurance to defy Mama, lift the spell, scream back at her.

I am a stronger witch than you, she thought. And you know it. I could lift this spell and there would be nothing you could do to prevent me.

But she could not do it. She could not bring herself to defy her mother in cold blood.

She only shook her head, telling her mother with her eyes what she must surely already know – that it would be madness to do this, madness to risk the fury of the Knyvets by ensnaring their son with a charm any hedgewitch could discover and undo. Then she turned and left, feeling the darkness swirling at her heels, as her mother snuffed the study lamp and stalked the opposite way down the corridor to her own bedroom.

It was only later, in her own room, as Rosa pinched the candle wick and undid the spell in order to rinse her mouth with cold water, swilling away the taste of the blood, that the realization came to her.

It was not Sebastian her mother had been trying to bind.

The spell had been for her.

3

Luke woke, sweating, and with his shout of fear echoing around the bare little room. His shoulder burnt with the pain of the brand, throbbing beneath the dressing, and for a minute he lay, his chest heaving, his skin wet with sweat. Then he turned with a shiver, the bedstead squawking in protest, and drew the rough blankets up to his chin.

But before he could close his eyes he heard the creak of the floorboards in the corridor and the wavering flicker of a candle flame illuminated the doorway.

‘Luke?’ said a gruff voice.

‘It’s nothing,’ Luke said shortly. ‘Only the old dream.’

His uncle nodded.

‘Well, you’d have to be made of iron not to have thought of them tonight. I know they were in my thoughts – and it wasn’t I . . .’ He trailed off. Luke turned his face away from the candlelight, knowing what his uncle had been about to say. It wasn’t William who’d hid beneath the settle as his mother and father were butchered before his eyes. It wasn’t William who’d stuffed his father’s neckerchief into his mouth to stifle his sobs, and watched as the blood ran down the walls and pooled on the rough boards, and the wavering shadow waxed high and black against the wall.

And you never saw his face? they’d questioned him afterwards. Luke had shook his head again and again, wishing there was a different answer, wishing he’d had the courage – not to save his parents, for he was wise enough, even as a child, to know that was not in his power and never had been. But the courage just to turn his head, to peep out and see the face of the man who’d sucked his father’s life from his mouth and vomited it, red and clotted, against the walls of their little house. But he had not. He had just lain, stifling his whimpers, mesmerized by the rise and shiver of the Black Witch’s shadow in the firelight, and the only clue he’d been able to give them was the cane that had rolled across the floor to lie against his leg, the cane with the ebony shaft and the silver head in the shape of a coiled snake. He’d lain there, trembling, as the hand in its black glove had groped closer and closer to his leg, like a monstrous black five-legged spider, creeping across the floor towards him.

And then – like a miracle – it’d found the cane and gripped it. The shadow against the wall straightened from its hunch and stood. Turned on its heel. Left.

The Black Witch had left Luke an orphan. It had left him with the knowledge of his own cowardice, his own powerlessness in the face of evil. And it had left him the dream.

‘I’m fine.’ He spoke more shortly than he meant to. ‘Leave me be.’

‘There’s nothing to be ashamed of, lad.’ His uncle stood in the doorway, the candlelight soft on his face. His voice, usually so loud, came low to Luke’s ears. ‘A man can’t be held a coward for his dreams.’

‘I’ve an early start. I promised Minna I’d shoe Bess ’fore she left.’

His uncle said nothing, only sighed. Then he nodded.

‘G’night, Luke. Sleep well, lad.’

I’ll try, Luke thought as he turned his pillow to the cool side and closed his eyes. The shadow rose up, wavering and black, and he fought down the fear that gripped him. You’re not a child any more. His fingers gripped the bedclothes. You’re a man. You will kill this witch and be done with it. She’s a sixteen-year-old girl, for God’s sake.

And then? Back to the forge. Back to real life. Back to the hope of finding the other witch. The Black Witch.

The dawn light was still thin and grey as he made his way across the cobbled alley between the house and the forge. Ice crackled in the puddles of smut-black water and his breath made clouds of white in the frosty air, but people and children were already up and about, making their way to their places of work, running errands, emptying the night slops into the street. He could hear the carts rumbling their way to Spitalfields market, or maybe to Smithfield’s, or Billingsgate, or others, further afield. From close at hand he could hear the muffled bone-shaking thump-badabadabada as the drayman rolled his barrels of beer off the cart and across the cobbles into the cellar of the Cock Tavern.

London was awake. Spitalfields never really slept anyway.

Luke unlatched the door of the forge, rubbing the last of the sleep from his eyes with cold fingers, and turned to the fire, pulling out the clinker and building it up again from the grey ashes of the day before. As he picked up the coal shovel, he winced, feeling the throb of his wound and the pull of the dressing beneath his shirt.

The forge was hot and roaring, and he was in a muck sweat from the heat of the fire and the effort of working the bellows, when he heard the clip-clop of hooves, and he turned his head to see a skinny girl astride a large bay mare coming into the courtyard.

‘Morning, Minna.’

‘I’ve to be at the dairy by six,’ Minna said without preamble. ‘Can you get her done in time?’

‘Yes, if you work the bellows.’

‘But I’ll get smuts on my dress! Who’ll want milk from a girl what looks like she’s bin up a chimbley?’