“Over here.” Laurel startled at Yeardley’s voice and turned to find him wiping down a spot at one of the tables with a handkerchief. “You two discuss the base,” Yeardley said. “I will gather everything I can find. The specimens on the shelves should still be clean.” Laurel nodded and Yeardley set to rifling through cupboards.

Fiona put the two bottles on the clear bit of table in front of them and told Laurel how she had come up with the base. It was much the same as the explanation she had given in the circle the first time Laurel was in Avalon, but after two summers of study, Laurel actually understood much of what she said. Fiona rattled off a list of ingredients she’d found in an old text: cured Joshua tree nettles, blended ficus and cucumber seeds, passion-fruit extract. The list was extensive and after a few minutes of recitation, Laurel stopped her. “I need to feel it. Can you pour a few drops in a small dish for me? If I touch the base in the bottle, I’m afraid the toxin will destroy it completely.” She looked over at Chelsea. “I’m going to need you both to be my hands.”

Chelsea glanced around and found a small, shallow dish as Fiona carefully unsealed the top of one of her bottles. She poured a few drops and Chelsea handed the dish to Laurel.

“I know that I have the base right up to this point,” Fiona said, shaking her head. “The text was very clear, and the whole thing came together perfectly. But the remainder of the instructions had been removed and no matter what I try next, I can’t seem to complete it. There’s something I’m missing and I have no idea what it could be.” She sighed. “The things I’ve tried. It’s ridiculous.”

As Fiona outlined her experiments and failures, Laurel dragged her finger through the small puddle of solution in the dish in front of her. Her fingertips were black and a little swollen, and she focused on the way Fiona’s mixture was reacting to the toxin in her body, how the toxin was reacting to the viridefaeco base. She felt the potential of the minor components, how they were suppressed by the major ones. There were several ingredients she would not have thought to put together – much like Klea’s vanishing powder, the viridefaeco base was a mess of tension. What it needed was an outlet. And somewhere at the back of Laurel’s mind, she felt like she’d encountered the proper element somewhere before.

It was the same feeling she’d had when she first analysed the powder Klea had made from her own amputated blossom – not that the missing ingredient was part of a faerie, in this case. She remembered that day with Tamani, sensing the things she could make from him – toxins, photosynthesis blockers, poisons. The serum Klea had made to defend the trolls against faerie magic; that had used faerie blossoms, too. Potions that used faerie blossoms did not help faeries, but hurt them. That wasn’t what they needed for the antidote.

Yeardley had told her when she first came to the Academy that knowledge was the essence of her magic – the place from which her intuition drew its power. The missing component was something she knew, something she’d encountered many times before – something she’d failed to recognise as a useful element, perhaps something Fiona had never encountered. That seemed to point to an ingredient that wasn’t common in Avalon.

“OK,” Laurel said. “I think you were on the right track with dried wheatgrass. Are there any varieties you don’t usually use? Maybe some they have to bring in from the Manor? Let’s go in that direction.”

Yeardley had gathered more herbs and supplies than Laurel would have guessed could survive the fire. But she didn’t question it, just set to work, directing Fiona and Chelsea in gathering and preparing additives, letting them do the actual work and testing samples as the potion progressed.

“It’s so close. Everything is here,” Laurel said after adding a tiny mist of rosewater, the only other thing she felt it could possibly need. She traced her finger through yet another sample. “It’s ready, it’s just not enough. The toxin is still overwhelming it. It’s like . . . like the ingredients are inert and they need something to activate them.” She sucked in a breath. That felt right. “A catalyst,” she said softly. “Something to unlock its potential.” But what?

Fiona shook her head. “This is why I had to move on to other projects. I even had the same idea you did – I travelled to the Manor. They told me humans have driven many plants into extinction over the last few centuries. The final ingredient must be one of those.”

“No,” Laurel insisted. “No, I know the final ingredient. It’s on the tip of my tongue. What grows in California that doesn’t grow in Avalon?”

“Laurel,” Chelsea said hesitantly. “Your face – it has dark spots on it.”

Laurel reached her hands up to touch her cheeks, remembering the way Tamani had done the same thing. How long had it been? It didn’t matter – she couldn’t think about it now.

If you can think like the Huntress, you can do as she has done.

The viridefaeco potion had been lost for centuries. But Klea had figured out how to make it again. What made her so special? She was always willing to push boundaries. She had probably tested both toxins and antidotes on herself, risking everything for her work. And hadn’t Laurel done that? Hadn’t she taken the poison into herself, to better understand it? But the more she understood the poison creeping through her body, the more she feared she couldn’t overcome it after all. Laurel picked up a fresh sample of the base and closed her eyes, continuing to run her finger through the solution, chanting her mantra in her mind. Think like Klea, think like Klea.