The rugby pitches were a generous sweep of land lying at the foot of a gentle rise. The little hillside beyond was crowned with ancient English woodland, which in April was filled with bluebells and on a day like today was probably not filled with vaping sixth formers. There had to be enough pitches for the First through Fourth XV to play home fixtures simultaneously—Chetwood would not have been able to host games otherwise—so the fields looked simply enormous as you came up to them. The grey mist of the rowing lake beyond was mildly picturesque in a Gothic sort of way. The combination of hilly rise and lake meant that these splendid school facilities, which got photographed in summer for the prospectus as a glorious expanse of green, were in fact a gigantic marsh. Canada geese browsed here most of the year. Only meticulous attention from the grounds team stopped the pitches from becoming approximately three acres of mud every autumn.

“Where are we putting the portal?”

“On the boundary, naturally,” said Walden, and set off across the grass. Her wellies went squelch squelch in the saturated mud underneath the green. What you wanted for a planar portal, wherever possible, was a sense of liminality: a border-place, an edge-place, somewhere where it made sense to say you were crossing from one world to another. An actual doorway was ideal—the division between mundane world and demonic plane, during Old Faithful’s incursion, had been marked by the front door of School House. Mark, bedraggled despite the red umbrella, looked hopefully towards the padlocked door of the boating shed. His trainers were muddy and his jeans were not doing particularly well in the driving sideways rain. “Did you ever row?” he said. “Cox, maybe?”

“No,” said Walden, thinking uncharitably And of course he’s a boatie.

“Shame. You’d probably have liked coxing. You strike me as the type.”

“You mean short and bossy?”

Mark faked contrition. “I’d say commanding.”

Ignoring the promise of shelter in the boating shed, she struck out for the jetty. It was cordoned off, with a NO SWIMMING sign—the open-water swimming club would probably start running again in spring—but she just stepped over the low fence. Mark said, “Ah, of course,” behind her as their footsteps sounded among the patter of raindrops on old wood.

“Technically,” Walden said, “Chetwood School does not own the lake.” There was even a village rowing club, with its own rather smaller shed on the far side of the grey water. “This is as far as we can go. Welcome to the boundary.”