Walden thought back to the morning of December 19. The date was stamped neatly in her memory: the day after the last day of the Autumn Term. If she got up right now and walked into her flat she would see the digital alarm clock on her bedside table, with the numbers illuminated red. The first time she’d woken up, it had been a little before seven, and Mark had not been in the bed. Then she’d woken up again, and it had already been half past eight. He’d come in with wet hair, wearing only a towel. Mistimed it, haven’t I.

An hour and a half between those two wakings. The door from her sitting room into the cavernous chamber of the thaumic engines had been left on the latch. Walden never had got round to asking Todd about it. Christmas—travel—family—all of that. She’d been busy. And it was the sort of detail you forgot about. Especially when you were already trying to forget the whole associated episode, as quickly as you could.

There were two keys to that door. Todd had one. Walden’s lived in a box in her kitchen next to the teapot. It wouldn’t have been hard to find—no, not hard to find at all. If Mark had any practice with instantiation, he could probably have cast a little charm to pick it up: shaped an inquiry from the keyhole, narrowed it to the profile of whatever metals keys were usually made from, and sent it sweeping through the flat. That was if he even needed to. If he hadn’t just poked around the kitchen while Walden slept, on the assumption that the key was probably around there somewhere.

Mistimed it, haven’t I? A little joke. Mark liked his little jokes.

He hadn’t mistimed anything.

But why—

No, that wasn’t the question. Walden was not employed as Chetwood’s Director of Magic in order to play detective. Motivations could wait. She had a hypothesis. She had no hard evidence for the hypothesis beyond some rather suggestive coincidences (Mark inviting himself round for drinks and waiting until she was two gins down before they went to bed, and that only after he’d established that he could get into the engine room from her flat) and a shadowy outline that bore an uncomfortable resemblance to exactly one person with access to the school site (a powerful adult magician, subtle, skilled, no morals whatsoever…).

The wastepaper bin next to her desk was overfilled, and so was the giant cardboard box of recycling next to that. Walden had to dig a little while to find the card. Plain white cardstock adorned with the Marshals’ heraldic crest. Arjun Ramamurthy, KMGC, Chief of Incident Response (SE England). A phone number and a mar.gov.uk email address. Walden set it on her desk and looked at it.