“I’d offer you a gin and tonic,” Walden said, “but we’re in loco parentis. I don’t think I’ll be able to sleep for a while yet, so if you’d like my room—”

“I’m doing a formal observation, thank you,” said Laura. “No. I’m going to sit up and observe how few demons there are in here and it’s going to make me feel a lot better. I was on a night shift anyway, I slept all afternoon, don’t worry about me. You should go to bed.”

Walden shook her head. “What I really want is a coffee,” she said. “What I’m going to have is a cup of tea. Would you like one?”

They had tea. Walden had a vast collection of mugs, because students kept giving them to her. She put the kettle on and fetched down one that said WORLD’S BEST TEACHER and another decorated with a cartoon of a cat.

“Do you want to talk about it?” Laura said abruptly. She was, Walden was coming to realise, actually rather an awkward person.

She poured boiling water over the teabags. “There’s not much to say.”

“I forgot you were an old girl,” said Laura. “The 2003 incursion—”

“Yes, I was there. I was in sixth form,” said Walden. “I admit that I should probably have mentioned it earlier. I do find it quite hard to talk about. How many sugars?”

“Two,” said Laura.

Walden had to hunt in the cupboard for sugar. Laura had definitely taken more than two when they had tea in the staffroom, so she got the whole bag and let her sort it out herself. Her own preferred brew was teacher tea: teabag mashed against the side of the travel cup for two minutes in the staffroom kitchen, splash of milk, rush off to your next lesson. She passed Laura the WORLD’S BEST TEACHER mug, sat down opposite her at the kitchen table, and took a sip from the cartoon cat mug. The tea was still much too hot. She already felt better.