Hecate left the sickroom just before midnight and made her way downstairs, stopping only to put on her cloak against the hard winter chill and to gather up the items she needed for what she meant to do. Dimity had promised to summon her if there was any change at all, but she still wanted to complete this task as quickly as she could and return to Ada's side.

She slipped through a side door that had led to the kitchen centuries ago, when it was separated from the castle for fear of fire, and out into the deserted courtyard. The sun had fallen below the horizon so long ago that she felt it had been night forever, an endless night that would go on and on into eternity. No doubt, she thought, it was the same way ancient people had felt when the solstice came. Whether she would feel the same relief they had felt when morning arrived was another question.

From her room, she had brought a drawstring bag, dark green velvet embroidered with magical symbols in silver thread, and now she reached into it and pulled out the first of a dozen thick, white pillar candles, hard and cold to the touch. She set it down on a paving stone, then added another one and another, forming the first quarter of a circle that would measure twelve feet across when it was complete.

"Miss Hardbroom?" The voice was young and uncertain, and Hecate knew instantly to whom it belonged. "What are you doing out here in the dark?"

"I might ask you the same question, Mildred Hubble." She moved on to the next segment of the circle, her hands still placing candles without missing a beat. "And I also might add that what I do is none of your affair."

"I know." Mildred kicked the toe of one scuffed and dirty boot at the stones. "I saw you from the window and I just...I thought you'd be with Miss Cackle."

"I've been with her all evening. Miss Drill is watching over her now."

"Is she any better?" Mildred's voice was suddenly even smaller and thinner, fragile as the squeak of a mouse in the frosty night air.

"No." Hecate put down the last candle, twisting its base against the stone to be certain it was secure, and then met Mildred's eyes directly for the first time. "But she's no worse, either. I spent all of last night brewing potions for her. Adder's tongue and angelica root, bittersweet and bay and comfrey. They haven't helped as I hoped, but perhaps they've done her some good."

Mildred nodded, accepting this, and then shivered and hugged herself for warmth as her gaze took in the ring of unlit candles. "Is that a spell?"

"Curiosity killed the cat, Mildred," Hecate said coldly. "Yes, it's a spell."

"What sort of a spell?"

Hecate stared at the top of Mildred's bowed head: the parting in her hair, the long, frazzled plaits dangling over her shoulders, the pale, vulnerable nape of her neck. Of course the girl was worried about Ada as well-they all were-but the incessant questions were driving her to distraction, and she could feel annoyance beginning to forge itself into a bright, hot coal of anger behind her breastbone. Knowing Ada wouldn't want that, and loath to disappoint Ada even in Ada's absence, she dug her nails into her palms, not quite hard enough to break the skin, and and answered Mildred's question with a question of her own.

"Which night is this?"

Mildred looked up at her, mouth slightly open in surprise at the abrupt switch from being querent to queried. "Well, it's the winter solstice. The longest night of the year."

"Yes," Hecate said. She picked up the hem of her skirt delicately and stepped into the circle. "It's also an auspicious time for magic, or so Miss Bat ought to have told you in your lessons this week. At the turning of the year, we can leave behind the past and make known our intentions for the future; we can ask for what we need and hope to receive it. Does that answer your question?"

She watched Mildred's brow furrow and then smooth out as understanding arrived. "You're going to ask for Miss Cackle to be made well."

"Exactly right. And now you had better get along to bed and leave me to it." Hecate turned away, shaking out her spell-casting fingers in preparation for lighting the first candle, and was startled when Mildred spoke up behind her.

"Can I help?"

"What?" She turned back to find the girl still standing there, the pointed, pale heart shape of her face in stark contrast to the dark.

"I want to help. You said before that a witch's powers grow every year, so mine must be stronger now than the last time I tried to cast a big spell, mustn't they? And we have the same intention, because we both care about Miss Cackle and want her to be all right, so that will make the magic stronger."

Hecate did not hesitate often, but she did now, studying Mildred as if she'd never truly seen her before. She had wanted to work this spell alone-had let Miss Drill think she was going to bed rather than telling her what she meant to do-but it occurred to her that Mildred might be the only other person in the school who shared her level of devotion to its headmistress. Everyone loved Ada, of course; her kind, forgiving nature and gentle humour made it impossible not to, unless you were her sister. But Mildred, like Hecate years before, had found herself lavished with nurturing and acceptance and care that she hardly deserved. Mildred understood , and in her fear for Ada's fate, Hecate was weak enough to want understanding, even from a thirteen-year-old. She thought of Ada lying far above them, hot as a furnace and still as death against the pillows, and made up her mind all in an instant.

"Come into the circle," she said, and Mildred smiled, relieved, and joined her, lifting her feet with exaggerated caution so as not to disturb anything.

"How does the spell work?"

"There are twelve candles in the circle," Hecate said. "You can think of them as the numbers on a clock face, or the months of the year, or the houses of the zodiac. We light them one by one, starting here, and as we do, we think of our intentions."

"Like wishes," Mildred said.

"No, wishes are passive. Witches don't wish for things, we will them to be. If we were working this spell under other circumstances, we would have a separate intention for each point on the circle, but this time we have one intention, and that is to save-" Her voice caught, and she forced herself to go on. "To return Miss Cackle to health."

"To return Miss Cackle to health," Mildred repeated firmly. "I'm ready. Should we take it in turns or both at the same time?"

"At the same time." Hecate beckoned Mildred closer, and the girl came and stood at her side. "And focus on the intention. We'll light the first candle now."

The courtyard was silent and still except for the faintest whisper of wind, and the flames barely flickered as they sprang into life one by one; tiny greedy flames devouring the wax and rising straight up into the dark. Hecate could hear Mildred murmuring something very softly with each new flame, but blocked it out and concentrated on her own thoughts of a strong and vital Ada, as she had been in the past and would be again in the future, always there to protect and defend and love. I bend the universe to my will. I create the outcome I wish to see. Return her to health. Her throat ached with the effort of keeping back tears as they lit the fifth candle and moved on to the sixth. Return her to health. Seven, eight. Return her to health. Nine, ten, eleven. Return her to health, and together she and Mildred lit the final candle and stood in the midst of a perfect circle of light.

"Is that all?" Mildred was nearly whispering. "Will she be all right now? Can we go and visit her?"

Hecate drew a breath that trembled more than she would have liked it to. "It may not work straight away. We'll have to see what happens between now and morning."

"It's so long to wait," Mildred said, and in the candles' golden glow, Hecate saw tears quivering on her eyelashes. "I wish-"

"So do I," Hecate said. "But the way to make morning come sooner is to go to sleep, so off to bed with you, Mildred."

Mildred's shuffling feet clearly wanted to obey this command, but the rest of her body resisted. "What about you, Miss Hardbroom? Aren't you going to bed too?"

"Not just yet," Hecate said. "Now I suggest you hurry along, before I remember that I ought to punish you for having been outside at this time of night in the first place."

"Yes, Miss Hardbroom," Mildred said resignedly, and clambered out of the circle in the same way she had entered it.

"Mildred!"

"Yes, Miss Hardbroom?"

"Thank you for your help," Hecate said. She inclined her head slightly in a respectful nod, as she would have done to a member of her own coven, and Mildred's tense, worried face broke into a grin that did more to light up the courtyard than all their candles put together.

"You're welcome," she said, and then, remembering what she'd been commanded to do, turned and hurried back toward the castle entrance, leaving Hecate on her own in the deepest part of the longest night.