“Is it safe?” asked Beth.

  The fifth attempt at making Vuillard substance had failed a few minutes ago. Beth had discovered over the course of the failures that the danger wasn’t limited to the initial explosion; quite often, there would be a second explosion a few minutes later. She’d been blown clean off her feet into a table yesterday, after which Isabelle had insisted on stopping work for the day in case she was concussed.

  So the moment Isabelle had indicated something wrong this time, Beth had flung herself behind the side-turned table that was serving as an explosion shelter, where she remained.

  “It’s fine,” said Isabelle. “You can come out now. Sorry about that. I think my hand shook a little when I was stirring.”

  Beth stood up cautiously, still half-expecting another explosion. “What damage?” she asked.

  “My nail paint is ruined. And I’ll need new clothes again. Don’t look directly at me, I’m not sure how well these remnants will hold together.”

  Indeed, Beth saw in the brief glimpse she allowed herself before jerking her gaze away to preserve Isabelle’s modesty that what had been a neat, practical outfit was now a set of charred, tattered rags. Beth shuddered to imagine what would have happened if Isabelle had been a normal person who burned when subjected to the kind of extreme heat these explosions provided.

  Then again, the way they’d configured the safety wards probably made it worse for Isabelle: instead of trying to suppress the explosion altogether, they contained it in the area immediately surrounding the cauldron for as long as they could. Since Isabelle normally managed a few seconds’ advance warning, that gave Beth just enough time to retreat to her improvised shelter. At the cost of exposing Isabelle to far more explosive force than was safe for any normal human.

  “Clean out the cauldron while I change, will you?” Isabelle asked, already making for the door.

  Beth’s entire body was shaking. She wasn’t entirely sure she could even walk over to the cauldron without her legs giving way. For about the dozenth time, she considered asking Isabelle to be excused from the project. She was sure she wasn’t actually increasing the odds of success by much, especially since a thirteen-year-old Isabelle had accomplished this feat solo. All she was doing was risking her own life and slowly turning into a gibbering wreck who flinched at the slightest sound.

  But she’d already raised that point with Isabelle twice, and the response had been the same each time: I won’t make you keep going if you don’t feel like you can. But I do need your help. And I do think what you’re contributing is meaningful.

  As the laboratory door swung shut behind Isabelle, Beth wondered whether she felt like she could keep going. She was rattled, and exhausted, but was she enough so that it meant her work was less precise? So far it hadn’t been, but this last explosion had been bad.

  “One step at a time,” she said to herself. Slowly, she walked over to the cauldron. It was made of a metal alloy with an extremely high melting point, so was still intact despite what they’d been doing to it. The same couldn’t be said for its contents, which had been largely incinerated. But specks of dust and ash still clung to the sides of the cauldron. And if they weren’t removed before the next attempt, round six would be doomed before it even began.

  Beth dragged the cauldron over to the drain and conjured enough water to cover its bottom, then began to meticulously scrub. Before this, she hadn’t been used to conjuring more than a glassful of water at a time. But for an alchemical project as precise as this, mundane water was far too impure to be used as a base for the substance.

  Thankfully, she wasn’t the only one responsible for providing the conjured water; Isabelle had been learning the spell too, and between them they could produce enough to fill the cauldron without risking magical exhaustion. Beth wasn’t sure quite how Isabelle had managed to actually learn any magic given her… unique circumstances. But that was just Isabelle, wasn’t it?

  She returned just as Beth was finishing with the cauldron, wearing what must have been her fifth or sixth outfit. Beth couldn’t help wondering if she’d run out of clothes before they succeeded. If they succeeded.

  “That done?” Isabelle asked, inspecting the interior of the cauldron. “Good.” She dragged it back to its place on the table. “Right. Sixth time’s the charm?”

  There was no such saying, but Beth appreciated the optimism at least. She didn’t respond, though, and Isabelle noted the hesitation.

  “We can do this, Beth,” she said. “I’ve been learning from every mistake. It gets easier each time, as each tiny part of the recipe becomes automatic. This will be the time it works.”

  She hadn’t said that any of the last five times. Beth wanted to believe that it was because she was more confident this time, because she really had been learning and improving each time. But part of her was scared she was only saying it now because it was what Beth wanted to hear.

  Still. Beth had enough hope to decide it was worth trying. “All right,” she said. “Sixth time’s the charm.”

  “Good,” said Isabelle. It was like she flicked a switch inside of herself, then, how swiftly she changed from the sympathetic girl who wanted to make sure her apprentice was okay to the ruthlessly focused alchemist. “Door is sealed. Safety wards – “ she reached under the table where the switches that activated the wards and modified their effects were located – “activated. Ingredient preparation – “

  “Finely dice worm-root,” Beth replied, doing her best to become a ruthlessly focused alchemist herself. “I’m on it.”

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  It took about fifteen minutes to slice and dice and pour and measure everything they’d need, except the half-dozen ingredients that would decay if exposed to the air for too long. Beth’s main task once the brewing properly began would be to prepare those at the exact moments necessary, though occasionally she’d need to take over stirring while Isabelle handled a difficult preparation or just took a moment to breathe, or keep track of the time when Isabelle had to focus too deeply for that.

  Once that was done, they filled the cauldron with conjured water. They took it slowly, knowing that conjuring a large volume at once would drain their magical capabilities far more than a little at a time. Beth had to admit that she was also stalling a little. Trying to delay the moment when they’d properly begin again.

  But inevitably, one conjuration at a time, the volume of water in the cauldron grew until it lapped gently at the three-quarters-full mark. Isabelle took a step back and let Beth cast the last conjuration-spell. Beth retreated a little once she’d done that. The risk of explosions was fairly low to begin with, but after yesterday she didn’t care to take chances.

  “Ready?” Isabelle asked, tucking her hair behind her ears and reaching for a small jar of golden sap.

  “Ready,” Beth lied.

  “Then let’s do this,” said Isabelle. In one smooth motion, she unscrewed the lid of the jar and tipped its contents into the cauldron.

  The process was long, complex and relentless like no other alchemy Beth had worked before. It took precisely two hours, eleven minutes and twenty seconds if it worked properly, according to Isabelle. None of their previous attempts had made it past an hour and a half.

  This one, though, was different. In snatched moments between tasks, Beth glanced at the clock and saw it tick up to the two-hour mark. She wasn’t as familiar with what she needed to do next, which scared her a little. She’d at least been confident that she wouldn’t mess up the early stages, but now… stars.

  Isabelle’s instructions were crisp and clear. Her master remained a model of perfect focus and efficiency. Beth was genuinely convinced in that moment that Isabelle was not entirely human, because no mere mortal could do what she was doing and remain so perfectly calm. Beth’s own hands were shaking, and she had to make an effort to hold them still enough that she wouldn’t ruin the preparation of the ingredients.

  “Are the seeds crushed?” Isabelle asked, without turning her head from her methodical stirring.

  “Yes,” Beth said, setting the pestle down.

  “Good. Tip them into the cauldron when I say… now.”

  Beth held the wooden board over the cauldron and scraped the seeds slowly in. The pale grey liquid within began to fizz as she did so. As soon as the last seed fell from the board, Beth set it down and ran for the improvised explosion shelter.

  “This is expected,” Isabelle said, still not looking round. “Count nineteen for me, starting… now.”

  Beth stood up and carefully walked back towards Isabelle, beginning to count aloud. She wasn’t certain of her timekeeping, with her heart pounding as hard as it was, but if Isabelle trusted it then she’d have to do the same.

  “Seventeen, eighteen… nineteen.”

  “Good.” Isabelle paused her stirring just long enough to snatch a jar and tip its contents into the cauldron. “If it steams, that’s expected – “

  A rush of steam did indeed emerge from the cauldron, smelling of pitch and coloured a dark grey that made it look more like smoke. Beth was grateful for the warning; that would have sent her running for the table again otherwise.

  The liquid in the cauldron gradually thickened as Isabelle stirred, occasionally switching her pattern or adding another ingredient or asking Beth to count a few seconds. Beth risked another glance at the clock. Two hours and seven minutes. They were close. Really close.

  She didn’t let herself relax. She couldn’t.

  “Leaves chopped?” Isabelle asked. Those particular leaves, soft and deep green, were the last ingredient Beth needed to handle.

  “Yes,” Beth replied.

  “Add them, and then count twenty-six… now.”

  Beth tossed the leaves into the cauldron and began to count.

  “Good,” said Isabelle when the twenty-six seconds had elapsed. “Fetch the moulds.”

  Beth blinked. “You mean…” Isabelle was referring to the wooden board with hemispherical holes carved into it, which they’d use to shape the Vuillard substance into the orbs they needed.

  “Fetch the moulds,” Isabelle repeated. She wasn’t going to say the words we’ve done it, then. Beth couldn’t blame her; while the final stage was unlikely to involve explosions, there was still a lot that could go wrong if they didn’t get the timing right. And it might even turn out that there was some technicality they – well, Isabelle – had missed which would cause the whole thing to fail.

  Beth fetched the moulds from the other side of the lab, where they’d been left to prevent their sustaining explosion damage. She set the board down in the space that had held her ingredients to prepare and the boards on which she prepared them.

  “Count sixteen,” said Isabelle. “Then fetch the ladle.”

  “One, two…”

  By the time Beth had fetched the ladle as ordered, she was more or less certain that they’d done it. Or at least this stage of the process. Isabelle was still stirring, but by now the grey liquid was thick enough that it was taking her considerable effort to move the rod.

  Isabelle was counting herself. She stopped when she reached thirty-three and removed the rod from the cauldron. “Right,” she said. “There should be no explosion risk from this point. We leave it for precisely three minutes, then start pouring it into the moulds.” She stepped away from the cauldron and tossed her hair back.

  That was when there was a knock at the door.

  “I’ll get it,” said Isabelle. “Get the potion of teleportation while I’m doing that.”

  Beth had brewed the potion of teleportation while Isabelle made preparations two days ago. It had been poured into half a dozen bottles, each containing four doses, and set safely aside. Beth walked over to where it was set aside while Isabelle crossed the room to open the door.

  Captain Morel stood on the other side, with two soldiers Beth didn’t recognise him behind him.

  “Isabelle,” he said. “The Administration Department would like to speak to you at once.”

  Beth’s heart skipped a beat. She’d just picked up two bottles of potion, and she nearly dropped them. But she kept her grip on the bottles and carried them over to the table.

  “This really isn’t a good time,” Isabelle replied. “We’re in the middle of a time-sensitive project.”

  “You’ve been telling me how amazing your apprentice is,” Morel replied. “She can handle it. Besides, the instructions were quite clear.”

  “All right,” Isabelle said calmly. “Beth, you know the procedure from here. We don’t want to waste the effort we put into this experiment, though you might need to adapt it a little. If I’m not back within an hour… begin testing. Got it?”

  No. Stars, no. This couldn’t be happening. “Yes.”

  “Good. Well then, Captain, lead the way.” And Isabelle smiled and stepped out of the lab.

  Beth blinked as the door swung shut behind her. She knew the procedure from here in theory, but she’d assumed she’d have Isabelle giving her orders at each stage. This part, they’d thought, would be tricky to get right with two of them. With just her, what chance did they have?

  And that wasn’t even the worst thing: Beth could read between the lines of what Isabelle had said. If I’m not back within an hour… begin testing.

  If I’m not back within an hour, use the orbs to escape without me. Because I might not come back at all.

  Stars, no.