The next three customers wanted a knife, a selection of herbs, and a crystal ball, respectively. The fourth harangued me at length about why the shop had been closed yesterday even though the sign said that it didn’t close until five and did I know how much travelling time I’d cost her? By the time she’d finished threatening to report me to the Office of Fair Trading and stormed off, a queue had grown up behind her.

Luna came in just as I was dealing with customer number . . . something or other, a bearded guy in a worn leather jacket. He smelt of beer and was taking much, much longer than he should to get the message that I was not going to sell him a love potion. “Hi, Alex!” Luna called over the sound of the bell.

“I already told you, there isn’t a formula,” I told the man. “If there were, Chanel would be selling it already . . . Where have you been?”

“Duelling class ran late,” Luna said, weaving between the customers. As she moved I saw the invisible silver mist mould itself to her body, clinging in a tight, dense layer on top of her exercise clothes instead of reaching out to the people in the shop. Once upon a time Luna could never have gotten that close to a crowd—she would have stopped at the edge and hesitated—but she’s been my apprentice for more than a year and she’s done a lot of growing. Not just in magical skill, but in confidence too. “I can use the shower, right?”

“Huh? Yeah, sure.” Luna disappeared into the corridor leading to the stairs up to my flat, and I turned back to the man at the counter. “Look, man, you got to help me,” the man began again.

“Look,” I said. “Even if I could make you a love potion—which, by the way, I can’t—have you any idea how unethical this is? You’re screwing around with someone’s emotions. It’s not something you do without a really good reason.”

Luna stuck her head back into the shop. “Hey, Alex? Is there supposed to be a fish out here?”

I covered my eyes. “No. There’s not.”

“What should I do with it?”

“Look,” the man started again. “You got to help me.”

“No, I don’t,” I told him, and turned to Luna. “I don’t care. Put it in the freezer or something.”

“Are you sure?”

“Why?”

“Isn’t that supposed to spoil the taste?”

“Look, man, I really need this,” the man said.

“I don’t care,” I said to both of them, then looked at Luna. “Put it wherever you’re supposed to put it.”

“Where’s that?”

“How should I know?”

“Well,” Luna said logically, “are we having this for dinner, or is it for something else?”

“I don’t care! Just get rid of it!”