She set the pen down and leaned back in her chair with a satisfied sigh. Her back ached. A glance at the wall clock told her it was nearly 11 P.M. Intruder, muttered the Phoenix, which made Walden look again and then smile: yes, the antique magician’s clock was possessed again, yet another invading imp. Imps were perfectly manageable with a little common sense. She honestly quite liked having them around. With any luck, the staffroom photocopier would have a reasonable inhabitant again before long, and everything would be back to normal; almost as if Old Faithful had never ripped through her school at all.

There was a knock at the door.

At this time of night? It could be anything—plenty of it bad. Walden felt like she’d summoned the problem just by being pleased with herself. She was already braced for the sight of Aneeta in tears in her puffy pink coat when she called, “Come in!”

“Evening,” said Mark, poking his head round the door. “Hoped I’d catch you still awake. Marking?” He’d seen the pile of papers and the red pen uncapped on her desk.

“Just finished,” Walden said. “What’s the matter?”

“Nothing at all,” said Mark. “I decided to run a late-night patrol—you never know, some demons keep odd hours—and when I was done I thought, ‘You know what, it’s fucking freezing out there and I bet Sapphire’s still at it too.’ Point to Daubery, I guessed right.” He came in and shut the door behind him. “Time to knock off for the night, come on. Any chance of a coffee?”

Oh, all right, why not. It had a bit of the undergrad feeling, someone knocking on your door late and coming in for a drink, but Walden found she quite liked the nostalgia of it all. Intruder, muttered the Phoenix again. Walden ignored it and said, “I don’t do caffeine this late, but I can fix you something. Come on through.”

Mark whistled when they went into the old Head’s flat. “Nice place. What’s through there?”

The door he was looking at was chained and padlocked. “The thaumic engines,” said Walden. “My long-term nemesis, second only to the Department for Education. Here’s the kitchen. I might have a tea. Or—” She had several very nice bottles in the drinks cabinet, and Mark had obviously already spotted them. “I’ve been victorious over my marking tonight. Maybe a G and T. You?”

“I’ll take a drop of whiskey in the coffee, if it’s on offer,” Mark said.

“I’ve got nothing special, I’m afraid,” Walden said, taking down the Bushmills. Mark waved that away, remarking that good whiskey didn’t go in coffee anyway; was Walden a gin drinker, then? What’s that—something local?